Running an automatic with nitrous is really hard on the internal parts. If you are running 500 HP it is easy to make a nearly stock C4 live well with it. Add a 150 shot to it and instead of a C4 that needs to take 650 HP you have a need for a C4 that will need to be built to take 800 hp.
Well you have an engine turning 6500 RPM putting 500 hp through your C4 and then you hit it with a sledge hammer of 150 HP! An instantaneous 150 additional HP - that C4 need to absorb that and then transmit it to the rear wheels.
It can be done - and I have done it many times.You will need some very special parts to get there.
1. Hardened and cryo treated input shaft.
2. Fully welded or sleeved forward clutch drum cryo treated.
3. billet planet carriers and four pinion planets.
4. High strength stator support and hardened pump gears.
5. Cryo treated shafts and drums.
6. Full manual valve body.
7. Anti-balloning converter.
8. Steel plate main case and bell cover.
9. 2 added clutches in each drum - Kevlar.
10. Kevlar front band
11. High stall converter
12. at least 35000 GVW cooler - maybe two.
use Mercon V because you will be running all Kevlar and Carbon friction materials.
Plan on spending a lot of money - $3500 - $5000 depending on what parts you end up using. This is a C4 that will hold up to the abuse for several - or more - seasons. Refreshing the transmission will be cheap in comparison to the initial cost probably $250 - $400.
Call Jay at Broader Performance and see if he will build you one - I know he does the cryo treating.. I don't know if he has the Australian made 4 pinion billet planetaries or not but talk to him.
Broader Performance Home Page
Tell him Paul from Seattle sent you - he is the guy I would buy my transmissions from if I didn't build my own.