Like you guys, I had poor luck with trying to seal the rivots.
I fixed mine, but some of it was luck. I used to have the "push in" style dipstick tube but found an NOS oil pan on ebay for an Econoline which happens to be the same as the Bronco (finding this was, to me, the lucky part). The new one uses a thread-in tube which is way better.
The next thing I did was drill the rivots out of the dipstick tube receiver thingy, remove the gasket, then weld it back to the pan. My welding is not perfect so I followed this up with some JBWeld to seal it. I capped the hole for the dipstick tube and filled the pan with water to make sure there were no leaks.
The next thing I did was buy a Dorman "Quick Disconnect" Fuel Line Repair Kit, part number 800-153, from Autozone. It comes with a metal tube that's the same size as the dipstick tube and threaded end that fits nicely into the oilpan, and an O-ring! I had to cut the metal tube to length, and bend it to get around the exhaust manifold.
Its been like that for a couple of years now and is one of the few parts of my truck that doesn't leak!
Newell