360 now 408 stroker oil pan still leaks!!

I have had this motor for ten years. It used to leak at the rear of the motor and I changed the gasket twice and still could not get it to stop leaking. Than this winter rebuilt motor to a stroker 408 and it started leaking in the rear again so I tried to go through and tighten all the bolts now it is leaking on the front seal. Before I take the pan off this winter is there any secrets that anyone has to stop the oil pan from leaking? A one piece ruberized gasket would be nice for our beloved small block's.
Help!
Pat Faley
1967 Barracuda Notchback
Peoria IL

It sounds like maybe you should just get a new pan? sounds like it is warped.