I have the NOS 5115 dry kit. I love it. I don't know if I'd slap a nitrous system on a motor with that many miles on it though. Unless you almost want to blow it up so that you can get the new motor underway.
But as long as you have good compression across all 8 cylinders & you don't really burn oil up, you could go for it. You'll definitely need to upgrade your fuel pump, one step colder spark plugs, retard your timing down to 8-10 degrees btdc...and an aftermarket ignition would help too. Even if you did all of those things, I still wouldn't go over a 100 shot, maybe a 125 shot if everything seems ok.