You use what ever engine you want in a car as long as you're happy with it and as long as you don't have to do too much butchery to get in. I have not seen too many 32's with engines other than V8's but I have seen quite a few Model A's and Track T's with 6's and 4's. Even saw a 31 roadster with a 12 cyl Lambo engine. Build what you like is the only suggestion. With some speed gear and dress up stuff a straight 6 can really look sharp.