The shop who did the machine work also threw in a set of piston rings. they are speed pro plasma moly rings. They are the "standard gap" rings that they claim need no file fitting. I pulled out a couple and measured their gap. The top ring measures .016"-.018" and the second 0.19"-.020"

I plan on running a good amount of nitrous, 200-250 shot. I'm thinking the ring gap should be more in the area of .020-.022" for the top ring and .023-.025 for the second ring. Is it a problem to file these rings? I'd hate to throw away a free set of rings, but if they're not right for the motor, then so be it. How about the gap size too? too tight, too loose?

 

Get the thousands per inch of bore and file them.Usually 'bout .004 x the bore size and a little more for hose.
.020 isn't enough for NO2.
Call Speed Pro and get their recommendation.