Gensets can go on any frame. Essentially you strip the locomotive down to the frame, do some frame strengthening, put 3/4" plating over the whole thing and start stacking components such as the pods, high voltage cabinet, cab, compressor etc.

The Sierra Northern is completing it's second unit in the Oakdale shops doing just that. In the Sierra's case, they used older GP9s to convert and are doing the work themselves. Aside from being quiet, comfortable, and fuel efficient, one big benefit from Gensets is they use DC traction motors (D77's). The Genset is by axle wheel slip control and is vastly superior to the units they are replacing for pulling power. When one axle slips, it is reduced in power until traction is regained. The subtracted power is added to the other traction motors real time, so you don't feel any lurching.

I would say its impossible to get sparks on the wheels of a Genset, but there was a case in Texas where the hand brake was left tied on a locomotive and not noticed, so I guess you can get a "slip" with sparks after all!