With the mods on my car listed in my signature, how much nitrous do you think I can run down the 1/4 mile without blowing my 100,000 mile stock 302 motor?
With 100,000 miles on the clock, i'd stick with 100 or less to be safer. I personally have seen 150 HP shots on high mileage 5.0's, but in most cases those guys ended up replacing head gaskets too after not very long. Good Luck!
300 is possible, but pretty much stupid. I know guys that have been using a 200 Shot for a long time on there high milage engines similar to yours without a problem. Of course it depends alot on the driver technique as well. A driver who dosn't know how to use nitrous will easily blow a hole in a piston or something else on his first try, even with a small shot of Nitrous. Overall I would play it smart and stick with a 150 shot, and insure you know how to proparbly use it. You failed to mention what you have for a fuel pump, I imagine you have upgraded that as well. If not, it would definetly be smart to do so, especially when nitrous is in the plans.
Seen a guy at the trackin a 89 lx run a compucar 250 shot on stock internals, block, intake and tranny. Just had the necessary mods: Big pump, 24lb. injectors, 70mm T/B, 3:90's, E/T streets. Low 12's