Subrails and cross chanels

[31steve]

I'm new here and starting work on a 31 roadster. The back half of my subrails and all 3 cross channels are junk and need to be replaced before I can start putting the body together. In looking at the ads for these from most of the suppliers, I notice that some are trim to fit, and some seem to be already trimmed with tabs and holes and ready to rivet on. Of course the price is higher for the ready to rivet ones. So my question is, are the more expensive ones worth it or do you still have to fabricate them to get them to fit anyway? Thanks, Steve