as far as I know 51 was the change year for huck to bendix. I have seem some early 51 year hucks on the swaps we do and I think GMC was a year lower or higher on the huck change.
With that said you can swap a huck for a bendix if you have the parts and backing plates. The upper spindle bolts on huck should be 7/16 while the bendix are half inch
If you have bendix you can use up to 59 for springs and parts
