440 to single plane or not?
The only thing that rear set of gears is good for is melting down tires. I'd go with the 3.91 gears and pinion snubber along with the 850 and keep the dual plane. If you're using BF Banana Skins or the equivalent change them for M+T ET street radial stickeys and hang on. That'll make that puppy grunt and dig in.
Terry :burnout: