My 390 had a persistent rear main seal leak. So I sent it to Keith to fix. He CNC'd the heads to Stage II, put in bigger valves, changed to a roller cam, swapped the block for an alum Pond, stroked to 482, replaced and balanced the rotating assembly, put it all back together, sealed it up, and dyno'd it.
By god it doesn't leak any more! Keith's the man!
Sam