oil leak between oil pan and timing cover

[old Chevy guy]

I've been reworking the old truck for awhile now. The chassis has been painted, the cabs been replaced, so on and so on. So while the motor was out I washed it up and threw some paint on it and changed all the oil gaskets. The oil pan and timing cover were pretty rusty so I swapped them out for some different ones, both were aftermarket neither new but in good shape. After I got it all in and running it was leaking from between where the pan meets the timing chain cover, a lot, like there is a gap. Today I took the timing chain cover off and was able to pop it right out without loosening the pan at all. Thinking that somehow the pan or cover was off I tried to compare the gasket fit on the old pan between the old and new timing chain covers and both fit badly. the rubber gasket is just plain to thin. Is this the wrong pan gasket set somehow or what's going on? I feel like back in the day I remember getting more than one set of rubber end gaskets when you bought a pan gasket, some thicker ones and some thinner ones, but I could be wrong. Has anyone else ever run into this? Its a 71 350 nothing high tech about it. Didn't leak there before shouldn't have ''fixed it'' I guess.