Well, thanks for all the advice (really!)... I can do without the vitriol. Why can't folks make their pitch for a solution, or even say why they think someone's solution won't work without questioning somebody's sanity or competency?
OP....Have you asked a transmission shop? I'm sure that they have seen this before. I too would be leery heading out for a long road trip with "will it hold" in the back of my mind. Stress you don't need.
Thanks CFD244! Here is the crux of the problem for me. I'm building this car for long distance road trips (read: several thousand miles for one trip), that's why I'm going through the trouble of installing a 4 speed automatic in a car that never had one (1970 Dart). I don't need a fix that might work when I'm crossing Southwest deserts in August! If this were simply a car to drive locally and occasionally, some of these suggestions would be worth a try.
I'm taking the trans back to the performance trans shop that built it for me and they will try to effect a permanent fix on the existing case (I like the idea of grinding it flat and then welding a new aluminum bung, or maybe an aluminum bung with a steel insert - do they make such a thing?). If they can't effect a repair they gave me a cheap price to swap all the internals to another case since they just rebuilt it (0 miles). I have a wanted ad here looking for another case, but no bites yet. The shop is looking for one, too. Fortunately all the case modifications to make this fit are in the 4th speed extension housing so I won't have to do that again.
Again - Thanks to everyone for their insights, I really appreciate you taking the time to respond. I'll let you know how it turns out.
