that makes sense! i have a leakdown tester as well. will try to borrow a bore scope ,but i find its pretty hard to see much with those. wondering about head gasket fire ring exposed to crank case causing a suck/blow condition??? seems odd to have happened seemingly so quick. its been awhile , but block was honed using washers under torqued head bolts ( to torque plate available) . 3 thou wear in cyl . new rings. ( it was a freshen up).
I don't think that washers under the head bolts would give you the same benefit of a torque plate. 0.003" cylinder bore wear, what's the piston to cylinder wall clearance with those pistons? If it's 0.005", then you have 0.008".