hello im new to this website, ive made a few posts on here asking questions and have always gotten great responces and advice from you guys! thanks everyone! im in the proccess of building a motor for my tractor! ive got a farmall M motor bored out with 4 and 1/8 pistons and sleeves, there the high compresion step head pistons for a 450 like what you would buy from tisco.. ive got a brand new 450 lp head and lp manifold,petronix electronic ignition, and new 450 cam im going to use in this motor. ill more then likly be putting the motor together this weekend if i get the gaskets this week.. im wondering what carb work i will have to do and what octane fuel to use ? i dont want to spend a week scratchin my head,cussing,and taking the bowl off 40 times and wrecking carburetor bowls drilling them out trying to find the best thing to work. i have a ihc carb off of a cobine motor that has the bigger main jet and metering stem in it that would bolt on the upper half of an m carb. i have a few different size venturies to pick from. would this bowl work or am i better off with something different or not changing anything to the stock carb? any help or advice would be greatly helpful! thanks guys!