56 Chevy Door latch issues

[craig32]

Greetings all, I'm having issues with the door latches on my 56. Most notably, that the driver's door comes open when I make some right turns that go uphill. I mentioned this to a guy at work and he asked if the door is still latched when it comes open - it is. When I first got the truck a year ago, one of the first things I did was get new latches, but they wouldn't work. If you look at one of the latches on ebay where the pivot is for the latch, it is about a half inch or better from the top of the housing. On my truck, the pivot pin is much closer to the top. After I put the new latch in, the housing hit the strike plate as if it were for a different model. Also on my latch, there is a pretty good groove in the moving part, maybe that's the problem?
So, apparently an aftermarket latch won't work - does anybody know where to find a good used original?
Thanks!
Craig