Take a look at this site:

http://www.curtmfg.com/Category/12/Multi-Fit%20Hitches

They have a number of univesal fit hitches and weld-on hitches. If nothing else, give them a call with your dimensions, they have numbers on the contact page.

They are a little pricey, but it's full list price, I'm sure a dealer can do better.

Frame specs:


http://chevy.oldcarmanualproject.com/shop/1948_51truck/51ctsm0202.htm

Heres a link to a discussion on the frame:
https://www.stovebolt.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=717568




1954 3600 Chevy Truck
"The Fake Truck"
In the Stovebolt Gallery
More pix on Photobucket