Jeff,
In my opinion QA1 shocks are the best cost/function compromise available., I have them on two Pantera's and the GT40.
The QA1's are available in single adjustable or double adjustable and when I contacted QA1 Tech they recommended what is now the 501 model, either DS501 (Single Adjustable) or DD501 (Double Adjustable). Note: These are the part #'s for bearing mounts, alternatively the 502 model is a poly bushing.
They have a 16 7/8" uncompressed length and 11 5/8" compressed and a recommended ride height of 13 1/4" to 14 1/2". They use a 12" long spring available in multiple rates. Summit Racing sell the shocks (bare shock bodies $220 single adjustable, $320 double) and springs at $71 ea. making obtaining springs for rate changes pretty easy. There is a mismatch in the eyelet size as the Pantera is M12 and QA1 shocks 1/2" so stepped bushing inserts require to be fabricated or alternatively ream out the Pantera shock mounting to take a 1/2 dia. bolt. I have a dimensional drawing to fabricate the stepped bushings if needed.
Spring rate recommendations seem to be as individual as Pantera's themselves dependent on your use. Larry regularly races (ORR and track) his narrow body Pantera and has 375# Fr with 400# Rr spring rates. Personally, I will start out at 350# Fr and 450# Rr and go with a 1" solid sway bar with the ball ends on what will be a wide body car that is intended to see some track use.
Lastly here's a thread with some measurements that might come in handy.
https://pantera.infopop.cc/top...ck-compressed-length
Julian