Slow build 71 Scamp 440
1: a serious teardown will be needed to diagnose unless you have someone you trust who is knowledgeable about such things. It may be easier to swap in a known good rear. I have seen people talk about using Cherokee rears, also stock 7&1/4 and 8&1/4 rears out of a bodies show up on craigslist near me often enough.
2: probably filler neck or sending unit gasket. Gas tank is easy enough to drop with a floor jack once it's close to E.
3: make sure to have a look at your wheel cylinders. Even if they aren't pouring out fluid there may be a build up around the seals indicating a small leak. I've replaced a master cylinder I didn't need to before:banghead: make sure to bench bleed it if you do replace.
4: there shouldn't be any slop in your kick down linkage but I don't know if that would mess with an up shift. Will definitely shorten the life of your trans so take care of it soon anyway. Also Check your band tension, you can do it underneath the car with the tranny still in. Do a search here and on other mopar specific sites for a how to, also definitely a filter and fluid change if you haven't already.
You're on the right track with this stuff!
