Check out www.calaisturbo.com.au this quite a popular thing for the VL boys, there is heaps of hybrid VL's out there. I am unsure of the cost, the cost will come down to how much of the work you want to do yourself etc etc. As for turbos and stuff, it depends what kinda power your after...... As for gearbox selection, an R33 box would be the go, they are strong because they are a GTR box just have no transfer case for the 4WD, and a brass button clutch or a double or triple place heavy duty ceramic clutch.
Hope this get starts to head you in the right direction...