I get my parts cheap from a local HL shop, I'm not much of a "buy-something-to-rip-parts-off-it" type guy, I just get what I need to do the job.

If you had to get a donor vehicle, I suggest Bulldog or Pershing, as they have a longer gearbox output spline than Tiger/Panther/Panzer, which makes it easier if you ever wanted to get rid of the stock plastic T34 gears and adapt metal HL into them. Still do-able with the axis vehicles, so yeah any or either

You can always make the electronics removable so they can be switched between tanks easily, thats how I tend to do it - then you're not disabling the donor tank, which will still be good for a static tank