One of the main problems with so many (almost all) of the late 70's early 80's Japanese TT's is lousy, super resonant plinths, platters, bases and ineffectual feet.
It will take some work, but if you put the time in, you should be able to improve that table quite a bit.
This is what I've found:
1. Plast-i-clay in every corner and joint of the inside of the chassis. A friend of mine has this (7 pounds)on every inside surface and does not use Dyna-mat. Same improvements, but it's ugly, if you care about the inside being ugly.
2. Dyna-mat on every possible flat inside surface as possible.
3. Dupli-color undercoat sound dampener can also be used in place of Dyna-mat, but not as effective. Can be used on platter to good effect, and can be removed easy too (with solvent).
4. Damping the tonearm is worthwhile. I believe Herbie has something that works.
Experiment with mats. I like the ISOkinetik Isomat 1 acrylic turntable mat. They're brilliant on glass platters, I'd expect them to work great on aloy, too.
I've read on some forums people claiming you can "over damp" a turntable. I personally believe this is BS. How can removing the maximum amount of unwanted vibrations and resonances be a negative?