Correct 4 bytes out of 65K to match a crc32 checksum
Disclaimer: It is not a review, and I am wild guessing.

The DrDobbs article outlines how the partial CRC could be recombined. I recommend to precompute CRCs of all fixed parts of the chunk, and let the GPU handle the rest. GPUs are notoriously good in number crunching, and you have at least 16K+ truly parallel cores on your graphics card. It is \$2^{18}\$ search space per core. Seems feasible.