A few questions

[Jesse 67 c-10]

1. I've been driving my truck to university every one in a while lately and I'm noticing that it will bog down quite a bit before it gets going when you step on it. goes good once it gets going but its hard to drive at low rpms. above 2500 it's ok. All new stuff, carb ignition. I have to run regular gas, (bulk farm tank) any tips on setting up my advance curves to improve this without causing pinging etc.? was running a bit better before. Another thing, my idle speed seems to change regularly, sometimes it doesn't want to go below 1100 and others its just running at 500, was thinking sticking advance? springs? new accel dist but who knows? probably related to above problem too. also accompanied by only bad gas milage, well that could be me too!

2. my truck has recently developed an annoying buzz under acceleration seems to be coming from about where the dome light is but holding it still doesn't stop the sound, any ideas or experience? things that could be causing this? seems to kind of resonate up in the cab

3. when I go around a corner, it sounds like there is something that slides from side to side in my fuel tank. fuel guage still works. Sounds like it goes from one side right to the other. nothing under my seat, something come disconnected?

4. recently noticed slight oil leak around pinion on rear end. not nearly a drip but wondering, can I change the pinion seal without having to re-set the gears? or am I going to be looking at a re-build in a bit anyways if this is leaking?

Probably simple solutions, I hope, any tips, personal experience or ideas would be greatly appreciated! Thanks for any help!
Jesse