What is your goal? Worker? Hotrod? If worker just replace with the 134. Need a bit more power go with a 172 or 192. Running engines are around if you look for $500 some less. What to build a hotrod V6 V8? get whatever engine you want and build an adapter plate. Going to be a lot more time and money than and 134/172/192 swap. I finished this 9n V6 with sherman step up conversion earlier this year and I'm have fun with but I do have other tractors to do work with. For Hp you can swap the standard engines with no conversion needed and get 34hp or 45hp or 60 hp or swap in a V6 like mine 150hp. It's your money so it's up to you which way you want to go