Handle<Value> merging_block(const Arguments& args) {
    HandleScope scope;

    if (args.Length() < 1)
        return except("You must provide one argument.");

    Local<Object> target = args[0]->ToObject();

    if (!Buffer::HasInstance(target))
        return except("Argument should be a buffer object.");

    std::string s = std::string(Buffer::Data(target), Buffer::Length(target));
    std::string block1_blob = s.substr(0, s.find("::")).c_str();
    std::string block2_blob = s.substr(s.find("::")+2, s.find(":-:") - (s.find("::") + 2)).c_str();
    std::string block1_diff = s.substr(s.find(":-:")+3, s.find(":-a:") - (s.find(":-:") + 3)).c_str();
    std::string block1_heig = s.substr(s.find(":-a:")+4, s.find(":-b:") - (s.find(":-a:") + 4)).c_str();
    std::string block2_diff = s.substr(s.find(":-b:")+4, s.find(":-c:") - (s.find(":-b:") + 4)).c_str();
    std::string block2_heig = s.substr(s.find(":-c:")+4, std::string::npos).c_str();

    BlockTemplate m_block1;
    BlockTemplate m_block2;
    std::string blockString;
    std::string blockString2;

    epee::string_tools::parse_hexstr_to_binbuff(block1_blob, blockString);
    std::istringstream stringStream(blockString);
    binary_archive<false> archive(stringStream);
    serialization::serialize(archive, m_block1.block);

    m_block1.difficulty = atol(block1_diff.c_str());
    m_block1.height = atol(block1_heig.c_str());

    epee::string_tools::parse_hexstr_to_binbuff(block2_blob, blockString2);
    std::istringstream stringStream2(blockString2);
    binary_archive<false> archive2(stringStream2);
    serialization::serialize(archive2, m_block2.block);

    m_block2.difficulty = atol(block2_diff.c_str());
    m_block2.height = atol(block2_heig.c_str());
    m_block2.block.timestamp = m_block1.block.timestamp;
    m_block2.block.parent_block.major_version = m_block1.block.major_version;
    m_block2.block.parent_block.minor_version = m_block1.block.minor_version;
    m_block2.block.parent_block.prev_id = m_block1.block.prev_id;
    m_block2.block.parent_block.nonce = m_block1.block.nonce;
    m_block2.block.parent_block.miner_tx = m_block1.block.miner_tx;
    m_block2.block.parent_block.number_of_transactions = m_block1.block.tx_hashes.size() + 1;
    m_block2.block.parent_block.miner_tx_branch.resize(crypto::tree_depth(m_block1.block.tx_hashes.size() + 1));
    std::vector<crypto::hash> transactionHashes;
    transactionHashes.push_back(cryptonote::get_transaction_hash(m_block1.block.miner_tx));
    std::copy(m_block1.block.tx_hashes.begin(), m_block1.block.tx_hashes.end(), std::back_inserter(transactionHashes));
    tree_branch(transactionHashes.data(), transactionHashes.size(), m_block2.block.parent_block.miner_tx_branch.data());
    m_block2.block.parent_block.blockchain_branch.clear();

    blobdata output = block_to_blob(m_block2.block);
    Buffer* buff = Buffer::New(output.data(), output.size());
    return scope.Close(buff->handle_);
}

Handle<Value> refill(const Arguments& args) {
    HandleScope scope;

    if (args.Length() < 1)
        return except("You must provide one argument.");

    Local<Object> target = args[0]->ToObject();

    if (!Buffer::HasInstance(target))
        return except("Argument should be a buffer object.");

    std::string s = std::string(Buffer::Data(target), Buffer::Length(target));
    std::string block1_blob = s.substr(0, s.find("::")).c_str();
    std::string block2_blob = s.substr(s.find("::")+2, s.find(":-:") - (s.find("::") + 2)).c_str();
    std::string block1_diff = s.substr(s.find(":-:")+3, s.find(":-a:") - (s.find(":-:") + 3)).c_str();
    std::string block1_heig = s.substr(s.find(":-a:")+4, s.find(":-b:") - (s.find(":-a:") + 4)).c_str();
    std::string block2_diff = s.substr(s.find(":-b:")+4, s.find(":-c:") - (s.find(":-b:") + 4)).c_str();
    std::string block2_heig = s.substr(s.find(":-c:")+4, std::string::npos).c_str();

    BlockTemplate m_block1;
    BlockTemplate m_block2;
    std::string blockString;
    std::string blockString2;

    epee::string_tools::parse_hexstr_to_binbuff(block1_blob, blockString);
    std::istringstream stringStream(blockString);
    binary_archive<false> archive(stringStream);
    serialization::serialize(archive, m_block1.block);

    m_block1.difficulty = atol(block1_diff.c_str());
    m_block1.height = atol(block1_heig.c_str());

    epee::string_tools::parse_hexstr_to_binbuff(block2_blob, blockString2);
    std::istringstream stringStream2(blockString2);
    binary_archive<false> archive2(stringStream2);
    serialization::serialize(archive2, m_block2.block);

    m_block2.difficulty = atol(block2_diff.c_str());
    m_block2.height = atol(block2_heig.c_str());

    std::vector<uint8_t>& extra = m_block1.block.miner_tx.extra;
    std::string extraAsString(reinterpret_cast<const char*>(extra.data()), extra.size());

    std::string extraNonceTemplate;
    extraNonceTemplate.push_back(TX_EXTRA_NONCE);
    extraNonceTemplate.push_back(43);
    extraNonceTemplate.append(43, '\0');

    size_t extraNoncePos = extraAsString.find(extraNonceTemplate);
    if (std::string::npos == extraNoncePos) {
      std::cout << "problema1" << ENDL;
    }

    cryptonote::tx_extra_merge_mining_tag tag;
    tag.depth = 0;
    if (!cryptonote::get_block_header_hash(m_block2.block, tag.merkle_root)) {
      std::cout << "problema2" << ENDL;
    }

    std::vector<uint8_t> extraNonceReplacement;
    if (!cryptonote::append_mm_tag_to_extra(extraNonceReplacement, tag)) {
      std::cout << "problema3" << ENDL;
    }

    if (43 < extraNonceReplacement.size()) {
      std::cout << "problema4" << ENDL;
    }

    size_t diff = extraNonceTemplate.size() - extraNonceReplacement.size();
    if (0 < diff) {
      extraNonceReplacement.push_back(TX_EXTRA_NONCE);
      extraNonceReplacement.push_back(diff - 2);
    }

    std::copy(extraNonceReplacement.begin(), extraNonceReplacement.end(), extra.begin() + extraNoncePos);
    blobdata output = block_to_blob(m_block1.block);
    Buffer* buff = Buffer::New(output.data(), output.size());
    return scope.Close(buff->handle_);
}

    var shareBuffer = new Buffer(blockTemplate.buffer.length);
    blockTemplate.buffer.copy(shareBuffer);
    shareBuffer.writeUInt32BE(job.extraNonce, blockTemplate.reserveOffset);
    new Buffer(nonce, 'hex').copy(shareBuffer, 73);
no 39 but 73
and in the function convert_blob
you have to use
get_bytecoin_block_hashing_blob

+    b.nonce = nonce;

+    if (b.major_version == BLOCK_MAJOR_VERSION_2) {

+        block parent_block;

+        b.parent_block.nonce = nonce;

+        if (!construct_parent_block(b, parent_block))

+            return except("Failed to construct parent block");

+

+        if (!mergeBlocks(parent_block, b, std::vector<crypto::hash>()))

+            return except("Failed to postprocess mining block");

+    }