all of the info you will ever need is on twinturbo.net
Engine blocks, crank etc are the same. Compression ratios are different, fueling system is different,injectors are different, heads also don't flow as well.
I have an NA block with girdle sitting in a nice place for a rainy day if I ever do something stupid to my current block.
A lot of new parts have come out in the last year to let us hit about 400-440 on pump gas with stock turbos/engine/transmission, around 500 on race fuel. But they don't come cheap. Just a simple selin dual intake, bigger injectors, electronic boost controller, chip, downpipes/testpipes and a boost controller and boost at 14-16 psi would be a lot of fun for relatively cheap. Most cars you will look at will already have a lot of this done.
Biggest thing to look for imo is brittle EFI harness, especially around the PTU area as it will cause ignition issues. These cars don't really have rust specific areas like the older Z chassis.
Btw if you buy one and put a front mount on it I will punch you in the stomach
Clean ones can be found for -9k. I paid on the high end for mine but it was truly mint for what I got.