From someone who has a half built LS1 into an R33 for track purposes, you really need to listen to Warps. You will instantly limit your choices of what/where you can enter to race.
You end up in sports sedans if under CAMS, or in the full on open categorys under anything else. From memory with drifting they've else banned engine swaps from different manufacturers.
That being said, they look great, and sound spastic. If I remember correctly, before the suspension was fully sorted on Stu's R32 LS1 he gave the keys to someone and it went a 1:02 or 1:03 around Wakefield.