Sorry about your buddy, Keith.
Something I've gotten into the habit of doing with nitrous, is to run a wide band O2 with a Lean Safety Shutoff switch. The last one I bought, came from Dave's Nitrous Outlet. Basically, you input a value for whatever you don't want the A/F to go beyond - let's say 13:1 for grins - If the WBO2 sees 13.00009:1, it interrupts the power to your nitrous system (I use the WOT switch's ground, interrupt it and kill the system OR if my timing retard is activated by WOT, I take out the nitrous solenoid itself), and saves your bacon on the motor. I stole this idea from a friend, and fortunately never needed it. I personally witnessed it save his engine twice due to electrical gremlins. He was trying to use the Lingenfelter two step when it first came out, with a progressive N2O controller, and those two flat would not get along (LS platform).
Also, I think nitrous is exempt from the "rich is safe" rule of thumb. Some say it can actually make things worse... All I know is, I bought that advice and it has served me well. You want your air/fuel to be correct at all times for the combo, what you DON'T want, is too much timing. TIMING is the key. I've never personally sprayed more than a 250, so I won't pretend to be a true expert, but I have certainly learned a lot about reading spark plugs, and tuning - through nitrous. I've never hurt any of my own, or others engines either. If you want to go faster? throw a bigger nitrous jet and pull more timing. DO NOT try to richen up, and add "just one more degree of timing" from a safe/good running tune. Maybe that makes more sense... Anyway.
I can't think of the guy's name on YellowBullet, Monty I think? If anyone is interested in learning how to run nitrous without destroying things, searching his posts would be an EXTREMELY good place to start. Best N2O information I've found, anywhere on the internet. Guy knows his stuff, and fortunately is one that is willing to share/help others.
I'm running an Induction Solutions plate on my 421" FE. Well, after all my crap comes back from Blair anyway. For the kit, I'll be using a stand alone fuel system with race gas for added security, as always. Something I HIGHLY recommend in a street/pump gas car. Cheaper than a set of pistons...