Some people will argue with me about which is the better platform, but the 92-95 civic hatchbacks and the Del Sol are built on the same chassis. Drivetrain and suspension parts are interchangeable between '92-'00 models, so there are tons of parts available for them as a result. The Del Sol would be a better choice given those options. Your options will be very limited for many parts on anything that's 15 years old, or older, so I'd steer away from the hatchback idea unless you went with something newer.

If you want boxy, get a dodge colt.