The Stovebolt Site Forums The Parking Lot Big Bolts 1972 c50 sbc 350 m465 single speed rear.....

It kind of sounds like your engine either needs a tune up or it is completely worn out. Besides a good radiator, you need to get the thing to put out its rated HP before you start worrying about bigger tires and faster gears. If you slow your engine down more, it will become even more of a dog.