Hey... I have a front stub for a 70 Belvedere, from radiator core support back to the torsion bar crossmember. It could serve as a model for any 68-70 B body application.I got it from a pal to use in the event that I wreck the Charger. I also have a spare V8 K member, various control arms, etc. If you want to use my stuff to mock up for fabrication let me know. The stub is easily transported in a full size truck.
The 70-74 E body is similar to the 71-74 B body in many ways, but as far as suspension, the B body went to a different K member in 73.