To put a 'gitso' in a C210 or Bo would be 'adding' to their woe's. The conty in any form is a stressed engine, fancy making it more so! And to think that all that could be in the hands of a low time pvt pilot!
Remember also it takes a huge amount of extra horsepower to gain a little more outright speed due drag, it's usually the climb etc that benifits more.
The idea of a turbine such as the C20 (Allison) would be perfect but oh the cost!
F