1971 Chevy Nova lowering...

[novajess1972]

I have a 71 Chevy Nova that (once they finally arrive) will wear Boyd Junk Yard Dog wheels in 17x8 on 235/45-17 front and 18x9 on 275/40-18 rear. Novas have that jacked-up stance and I want to lower it to compliment the new meat. I plan to use Hotchkis lowering springs up front, but what about the rear? Call me cheap but I am trying to avoid purchasing the leaf spring lowering kit for $375. I have seen the more "cost-effective" lowering blocks, but how do you know how wide or thick to get them? It would be simple if they just said "lowers car 1.5 or 2in" but they don't. Please help. Thanks.