I'll go along with these guys and say to stay with the 6 cylinders. They are good engines.
I am a V8 small block fan. If you are going to drop in a SBC, just go with a 350 because of the cheaper to build parts. You can make it look like a stock 283 if you like.
I have 283's, 327's and 350's. They are similar enough where most people don't know the difference. I love the 283's and 327's because I like to be away from the "norm".
If you are just driving it, either a 283 or 327 is just fine. They are beautiful and reliable engines and can be easily used with 2 or 4 barrel carbs. Just keep the carbs small.
If you want to build HP, use a 350.