I too have, and am currently, looking into how to do a shaft drive mc engine in a true LOCOST way.
Spending money is the easy way. A custom small reverse rotation gearbox is very simple and can be built with any gear reduction you may want to work with whatever diff ratio you have. But unless you have access to the gears and shafts required it will get expensive fast. Once you add the desire to have reverse gear also though, the complexity goes way, way up, as does the cost of course.
You can go with Quaife or Nova Racing Transmissions but both are well over $1,000 delivered. Nova sent me a nice drawing of a reverse rotation gear box that does include reverse built just for this purpose. I think Quaife can build one also but at even higher cost.
The Reverse rotation Ring & Pinion gears available for the Toyota 7.5" is one way. Although probably not the best way as robertwa said.
I am leaning towards just running an inverted rear end and see how much the whine bothers me while looking for another alternative.
Grassroots Motorsports magazine built a custom reverse rotation gearbox with reverse gear for their Bezerkely project and it is very instructional to read how it self destructed the first autocross run. The article on the gearbox explained how many hours were involved in the design and construction of it.
I plan an electric reverse to keep the cost down as I already have the starter motor to use for it.
James
