First off there are seperate systems for return and non-return type fuel system. Make sure you have the correct one for your vehicle.
A 75 shot on the Explorer would give it a good kick in the arse. The only problem is you WILL want more later.
Find a system that will work with your TPS system. I agree, a dry kit for your set-up would likely be best. It's far better to have a larger pump in for better control of the fuel pressure than it is to find out you may go lean. However, GENERALLY, a stock pump will be sufficient up to that level.
It is best to have a tune to go with it as the others have stated on here. MOST Systems are set-up for 93 Octane pump gas. You need to insure thats what your tune is set up for if thats what the system calls for.
There are many factors as far as the performance of your vehicle with the N20. Mods, Tune, weight, power levels as well as all aspects of the system you are running such as recommended bottle pressure, how full or emty the bottle, delivery of the Nitrous, and so many other varibles. A 75 shot if done correclty should put you at least 5/10- 9/10's and possibly better at a track with traction and everything working properly. AGAIN, lots of things to take into consideration but thats a possibility.
Just remember as was previously mentioned, these engines will take this rather easily on on a part time basis. You go beating on them all the time with it and be rest assured, they will be beat back. Occasional use on a stock motor that is set up accordingly should last you qutie a while. If not used properly, it could be destroyed immediately.
So have fun but be advised.