anyboby smallblocked a 70's colt?

It's been a while, but I've seen small blocks in Colts and Arrows. But I would strongly suggest frame connectors as well as an 8 point cage, all tied together, especially if it will be raced hard. Otherwise, you WILL tweak the chassis and body. It will likely be nose-heavy, so a stiff chassis will help weight transfer. Those little cars just weren't designed to handle V-8 power and do have a reputation of being squirrely, even done professionally, because of the short wheelbase.