How can I make my 79SB handle better?

I have a 71 SB and I had a shimmie problem with mine. When I first got the car, it had old 5 spoke craigers with adapters on it and it shook a lot. I then put some stock wheels and worn out very old (sat on flats for 7 years) 165 sr 15's on it. The shake wasnt quite as bad, but still there. Now I have a good set of 185 65 15's on it and I have almost no shimmie what so ever. At certain speeds, I get a slight vibration and I think I can fix that with taking the wheels off and turning them 180 degrees and putting them back on. If it was me, I would check all the components in the front end and then replace my tires or at least get them ballanced and go from there. The shorter, wider tires helped my cornering ability a lot. Someday, I will upgrade my wheels, struts and numerous other things. Just my thoughts, good luck with it. Randy