Exactly, you could mount your shifter almost anywhere.

The Ultima website rates the 140ci v twin at 175lbs!
165bhp but these trans also sit behind turbo drag v twins
http://www.ultimaproducts.com/transrsd6speed.html

I wonder if someone knows something about these boxes
they are cheap at 6-700usd on ebay, gearset replacements at 500usd

2kw starter could be used from ultima
just needs an adaptor for an A series auto bellhousing
flange for the prop and clutch spline and input shaft considerations etc

The whole cost could be easier than sourcing and rebuilding old T50 toy boxes
buying a kit for them and fitting them only to have a H pattern.