Rc10 gold tub advice needed please.

[bald eagle]

I recently bought an old rc10 from the USA. Car arrives in a bit of a state etc so my intention is to restore it to a car that's not totally original etc but more of a pleasing to the eye car.
Problem I have is, car arrives with stealth gearbox on a 'b' chassis which is in quite a sad state all scratched etc, so I bought a gold pan chassis 'a' stamped, In quite nice condition, the 'a' chassis doesn't come pre drilled for the stealth box, should I drill the chassis and countersink to fit the stealth, or try and find a complete old 6 gear gearbox??