First: the absolute positive best way to get a racecar is to
buy a good one that is already built, rather than build one yourself,
even if you have to spend some time tweaking, you generally
get the benefit of a bazillion hours of free labor and parts
at 40 cents on the dollar

Second: the E36 325's are exceedingly popular in ITR, and the
ticket to the front row, at least here in the northeast, which
seems to be the best ITR market so far... you could run it in
ITS with an SIR, but nobody around here does anymore

good luck!