Weird Tach Problems

[TypeSL_T]

I am driving my dad's '83 while I am fixing my Saturn, and I told him that I was going to look at a few problems he is having. Problem is, some are kinda weird. For instance, when I am giving the car some throttle like when I am getting on the interstate, the tach will kinda bounce around. And normally I wouldn't care, but the car has been running pretty rough as of late, and seems to have lost some power. Could anyone help me figure out which direction I should be going with this? I have been told that I should look for a vacuum leak for the running rough, but they are clueless about the tach issue. I was thinking that there may be a problem with the distributor. I don't know very much about working on carbd stuff though, so maybe the vacuum leak would fix all my problems. Sorry for such a long winded post, but thanks for any assistance.

James