Mike:
I've had a few engines where the timing cover and the block had a small "ledge/gap" as you have, put a good dab of RTV on the ledge before installing the gasket to fill in the gap........
I've also had very,very good luck with the plane jane cork
oil pan gaskets and thats all I use. The advise to make sure the pan holes have not bulged up is right on, make sure they are all flat, take a hammer and something to back it up and dolly them flat again before installing the pan....
I like to "smear" a very small amount of RVT on the clean block bottom and put the cork gasket on and let it set up, then once it has dried, install the pan, that way the gasket doesn't move around when installing it.....with the cork gasket I snug the pan bolts down and then let it sit for a few minutes and re-tighten, I usually do this a total of 3 times as the cork gasket will "give" some, be careful not to overtighten, because then you smash the gasket and it'll never seal up...
Using this method, I can not remember the last time I had a leak........
I tried the one-piece rubber gasket (MR. GASKET brand) and it leaked like crazy, went back to the old cork gasket and never leaked a drop of
oil on the same motor.......some have had good luck with the one-piece gasket,some haven't, I think it's a hit and miss thing with them.........
David