I'm going to be in the same situation as soon as the engine & trans are back in the car. I got a new Strange S-60 from Dr. Diff, but he told me to measure things first before I order a new driveshaft, rather than replacing it w/ an OEM-length shaft for an E-body Dana 60 (if that's even possible).

3" vs 3.5"? Not sure how much clearance my bolt-on driveshaft loop has w/ a larger-than-OEM 3.5"...

Mild steel vs chro-moly vs ???

3800#-ish w/ driver, 650+ HP & 600-ish torque, 727 foot-braked, targeting low 10s in the 1/4.