[fast1075]

Watch your quench closely. Run it as tight as you dare. I have no 250 engine build experience, so I don't know how much the rods and pistons "grow" at speed under boost. I ran my old school KZ-1000 motors at .040 with stock rods, and at .035 with Falicon rods.

Poor quench means instant detonation under boost. I think I was getting some pretty good cylinder pressure running .050 nitrous and .052 fuel jets on a 1425 motor with 900 psi bottle pressure and 9 psi fuel pressure.

I kept it sealed with ARP studs and Power Rings. (O-Rings did not get the job done). Oh, and I had to make aluminum base gaskets. Paper ones "squished" out from the clamping force.

Nobody makes Power Rings as small as the 250 bore, but anything can be made, and you could use a stock head gasket (with some mods to it). But you would need a skilled machinist. (I just checked at MTC Engineering, and they don't have power rings smaller than 78mm, but I bet they can make some in your size.)