General questions from a new owner

Hey guys! I'm a new owner of a '74 Duster. I may have "met" some of you on the welcome wagon already. I have a few questions that I'm hoping some of you can help me with.

First: the front wheels seem to be farther apart than the rears, leaving the rears looking more "tucked in" than the fronts. Is this my imagination? Or were these cars actually built this way? It was an original 225 car, and the original rear end (7 1/4, I think?) is still on there, if that's relevant. Is there a common way to remedy this without using spacers?

Second: My rear is sagging like I have a trunk full of cinderblocks, and I can't afford new leaf springs right now, so I was looking at some helpers from JC Whitney for 50 bucks. Does anybody have any first-hand experience with these? Will they pick up the rear and help with the stance for now?

Third: My U-joints are making a hell of a lot of noise. They clunk when I shift into gear and when the tranny downshifts on decel, and I'm almost positive they're the source of the rotational squeaking coming from beneath me on acceleration. They have grease fittings, but it looks like I have to remove the driveshaft to access them. Should I just replace them when I take the shaft down, or do you guys think pumping some grease into them will cure my problem?

Lastly: There is some oil leaking from where the bell housing meets the engine. My first thought on this is that the rear main seal is bad, but the guy I bought it from still swears that it was changed about five thousand miles ago. Could my leak be something else back there? Or is the guy just lying to me for no reason?

I know this has been a long post, so thanks in advance to anyone willing to share his thoughts and opinions.