E30s have 3 different engine sizes... 318, 325, or the M.
Have him get a 325is.
dont get a 325e (super eta)
i recommend an 89-91 so you have plastic bumpers
as for after market stuff...
suspension is key
have him do shadowlining(painting the chrome/silver side trim black)
other than that...
if he had a few grand, he could get a stroker kit
a lot of people turbo those cars too
or even drop a e36 motor in
suspension would be my first mod
e30s are solid cars, made better than e36s