C-10 v. C-20 frame

[panhandler62]

Is there a difference in the shapes in the C-20 and C-10 frame in the rear axle area?

I bought bolt in c-notches a few months back (I really don't remember if I specified that I have a c-20 or not) and finaly got to working on that part of the restoration this weekend.

The things really don't fit well. I expected them to flush up to the outside of the frame (once the notch area was removed, of course) and they really didn't. There are some gaps and the bottom plate hangs outside the frame by about 1/2 an inch at the front. They are close enough that wanging on the one I have installed with a BFH got it mostly matched up but not close enough to make bolting it make sense. I welded it on where it does hit the frame and I'll be doing some trimming and making gussets and reinforcements to finish. With the peice not fitting flush; I didn't want to just bolt it up, leaving gaps for rust to sneak into between the peices.

Not a show-stopper in the end, just kind of wondering is "sort of" fits is normal here, if I bought c-10 parts when I should have bought c-20 parts or if I just got a set that wasn't quite right?