Get a 635i the M30 engine is fantastic easy to work on etc. Watch out for cracked cyclinder heads they are a pain in the ass.
I had a M30 in my E30 it was great, tonnes of power
I like the old 6 series as well its got this majestic look to it. I also like the E28 5 series, you can get that in a 535i as well. They are very juicy though.
300zx is a nightmare to work on, just look inside the engine bay and imagine trying to fix anything on that! Also parts are expensive, another juicy choice.