Brothers sells a C notch kit for 99.00 that you should be able to get someone to weld in for a reasonable price.
https://www.brotherstrucks.com/1955-...tinfo/CNK5559/ A lot of the cost in something like this is prep. If you have the bed and fenders removed, have the frame all clean and wire brushed and maybe cleaned up with a flap wheel or other metal cleaning disk so all they have to do is cut, fit and weld it could save quite a bit of money the total cost should be lower. The less non actual cut, fit and weld work someone has to do the lower the cost.,
The other option is to call or email
http://www.mcgaughysclassic.com/home.html and ask if they either have a bolt in or one of their bolt in units can be used with limited mods. They were just about the first ones making bolt in C notchs and turn out some pretty decent but not cheap work.