What parts (rockers, springs) of the kit are compatible with SBC earlier than LT1(LT-1). I can never keep that straight.

I don't know off the top of my head but I can tell you the cam is compatabile with gen I factory roller blocks and the springs are compatible with Gen I heads when machined (ZZ4 heads are AL L98 heads with LT4 springs).

The kit works great in L98s. Anything else, I don't know about.

I guess what I need to do is id the heads that were used on the remanufacture.
For all I know they are L03 tbi heads from the factory. They are center bolt though.

As an alternative, how about the LT4 production cam?

I have a remanufactured engine in my '91 RS and identifying the heads may be a problem.

How would I go about identifying the type of head, rockers in it?

I'm not afraid to pull the valve covers to look around.