Just in case this is relevant:
A 6400 will have a handbrake lever for parking brakes near the floor shifter. The 50 pickup will be foot operated. The donor cab will require a new hole in the floorboard and pedal shaft seal (felt holder) which I think is spot welded. The 50 parking brake bracket, brake knob and rod, underfloor brace/bracket and associated linkage will be removed and installed on donor cab. Personally I like the parking brake lever better but that would require some fabrication.
Good info.
The foot operated parking brake system could be swapped over to the big bolt cab. It would require a square hole for the pedal itself and the locking shaft also requires a round hole on the toeboard. There's a reinforcing piece for the foot parking brake that bolts to the toeboard that has the pocket for the felt seal for the locking bar, as well as captive nuts to bolt the left side inner fender to. Not sure if the big bolt cabs have a similar reinforcement piece that the inner fender would bolt to.
If the original cab can be saved and repaired (doesn't look that bad IMO, as I have repaired a worse one) that would be the best approach. Definitely check into the serial number tag situation for your state. Using the original cab would take care of that issue.
