Actually you'll want the 80430. There is a long thread on here about 2-stage pistons that got me intrigued. Initially I ran a different brand and was happy with the performance, but not with the fit, so I switched to the RPMs. I'm running a T4.1, and use the red pistons with 25wt front and rear. When our local "fast guy" drove my truck (per my request to see if it felt like it pushed to much to him) he kept asking my about my suspension because of the feel. He's running a b4.1 with reds and 30wt now. I'm not sure if he has run any lighter weights for testing or not. 30wt felt to heavy to me, as my truck would bounce down the rougher parts of the track (just like it did with the stock AE pistons and 30wt). With my current setup, the chassis stays level and the suspension works it's butt of in the rough areas. So, my opinion is that the real advantage with the 2-stage pistons is when the track gets rough, my lap times stay more consistent whereas the others slow a little more due to the bouncing. When the track is smooth, there appears to be little to no advantage as I see it.

Do they last forever? Not sure yet. They appear to be made from the same material that RPM uses for everything. Based on that, they probably will last a LONG time.

What kind of washer setup do you use at the shock body bottom? Are you talking about the spacers for limiting? I run the stock numbers and am happy with the results thus far. However, I haven't done any testing in this area.

Can you safely go with some pretty stiff springs using these? If you want to, I don't see why not. I tried silvers in the rear because my truck is a little heavier in the rear due to an oversize aftermarket wing, but I ended up going back to green.

LMK if I can answer/clarify anything or help in any way.