Re: HI All, two not so simple questions.
I agree on the Dax engines, I've bought 4 of his bottom ends and they all tuned out really good engines. I put mine thru a lot and they're just rock solid dependable.
Since I'm always trying to get the most performance out of the engines I build I use the best parts I can find to put them together, the Dax bottom ends have proven themselves bullet proof at 5+ hp and 10,000+ rpm.
For the GRU you speak of, a jack shaft is probably your best bet, it can be as simple as a shaft with 2 pillow block bearings and a set of spockets, the input sprocket needs to be bigger than the output, but both sprockets can be set up on the same side of the shaft, so let's say you need twice the torque to the rear wheel, you would want a 20 tooth input and a 10 tooth output to the rear wheel, your top speed would be cut in half, but your torque to the wheel would be doubled... great for pulling or hill climbing.
You could use a 15 tooth input if that cut the speed down too much and still come out with excellent pulling power.
This would be a viable alternative to running a huge rear sprocket.