I agree with the guys saying a 3" chop. I did a 3" chop on my fathers '31, and unless you are a very small person, you aren't going to be comfortable.I couldn't imagine a 4" chop..Also are you channeling it?If you channel it, plan on modifying the frame.I don't agree that it is a straight down chop. There is taper in some areas that have to be dealt with. As far as the price, it should be reasonable compared to most. It took me about a weekend to get it layed-out, cut, welded, and glassed.I hope this info helped you. Good luck!