all right need advice i got a 86 iroc-z 383 stroker got a t56 trans ford 9in read end i cant hook at the track no matter what tire i throw on it, it is stiff as a skate board thinking about trying different rear springs the ones on it are only 9in long seams to short to me any suggestions on a spring? or will it even help?

 

Get a set of real bad wore-out stock ones out of a 6-cyl car.

Sounds like you have "lowering" springs of some sort; obviously those have to start out shorter than stock, but also have a MUCH higher rate (stiffness) than stock, to keep the car from bottoming out all the time. Wrong altogether for a strip car.

 

Sounds more like shocks and lca geometry than springs. Any springs can work. Stock z28 is fine. Front shocks are important for transfer as well

A manual car is goona be difficult to get to launch hard

 

What he said... for the most part in a drag type application the spring just holds the car up when the suspension is not exerting a force on it from acceleration. Any reasonable spring for an 3rd or 4th gen will work.