[NovaMan]

3* down is probably good for a factory 3 or 4 link, but leaf springs tend to need more. Slide-a-Links may do a better job of combating pinion angle change, but slapper bars usually like 6-8* down.
The other day, I saw a 70s Ford pickup driving down the road. When he accelerated (not really getting on it much), I could see his axle housing twist up quite a bit. Granted, he had lift blocks and no traction bars, but he wasn't launching to a 1.5 second 60' time either.