I'm putting a 250 in my 51 for a driver as a 250 does unleaded and the parts as well as the motor are penny wise. Any in put other than the bell houseing mount and 12 volt and radiator modifications? Thank you. The truck was a piece of rust whith a 51 some where in there 3 years ago so as far as ruining it, its already been there. and the repro parts aren't perfect. Its a driver with a stock frame and body. In other words I don't feel a 250 is a hack but a rebirth of some thing that could go back to the earth or find me. So have any of you done this? Way thank you! cool O. The town of Sedro Wooley mamouth thanks you all as well.