Before taking the bugeye all apart I exchanged the origional 4.22 for the 3.9. I have the 5 speed conv. and have changed speedo's for the later midget, so the speed is correct ( I've gpsed it). The bugeye is a lot less busy at 75 to 80 mph and just is more comfortable. I'm really looking forward to this next summer, potentially changing to the 4.22, and 3.7 just to see the difference. Once you've done it, it really isn't a mistery, in fact quite simple.