It depends on how big of a lift...
Are you talking about making a non-ZR2 sit like a ZR2? I don't think ZR2 leaf springs are actually any bigger than a regular S10 leaf, I'm pretty sure it just has to do with where the mounts are located. I'm pretty sure that is the main difference in general, the location that suspension stuff mounts to the frame. The A arms might be longer in the front too, I really don't know for sure though.
Here is a good page to look at if you don't know what kind of lift to get.
Hope I helped
(This should probably also be in Chevy Tech)