The clunk is almost certainly track rod bushings. Next time you get under the car, look at the front suspension. The track rod runs at an angle from the lower control arm to the body. If you pull the rubber cover back, you will find that the track rod is not properly centered on the bushing or other obvious signs of movment and wear. These are a bear to replace youself, but it can be done. Wait until you have a floor jack and jack stands, though... the car has to be up in the air.
The vibration can be either the bad track rod bushings allowing fore and aft movement of the front control arms, or the tranny mount and/or center bearing support on the driveshaft. The tranny mount will also cause vibration on acceleration, a distinct low frequency drumming of the floorpan.
A bad center bearing mount will also cause vibration on acceleration, but it will be centered at the rear edge of the driver's seat on the tunnel. If you put you hand on the side of the tunnel when you get vibration and the tunnel is obviously the source, you need a new bearing mount. The other check it to try to move the shaft in the mount with the bolts tight -- if you can visibly move the shaft around, the mount is shot, it should be fairly stiff.
Tires can also cause vibration, too, so take a good look at them.
Cracked plastic upper hose nipples are a common problem. Green antifreeze seems to make this worse, but the real cause is embrittlement of the plastic, and the only cure is radiator replacement. You CAN put a new tank on, but the aluminum radiator almost always refuses to seal properly (I've done this, doesn't work!). I've had two identical rads blow a hose nipple, one while I was working on it (luckily!), the other in my sister's Volvo 740 Turbo, she ended up with a new head and radiator.
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!