My '60's U Joints do not have grease fittings. I have no idea how old they are but I've had the car for 9 years. They are NOT making noise but would it be
smart to replace them preemptively?

 

If you do, use Spicer LIFETIME joints - they will be solid, & most of them are made in the USA. Sold is the strongest.

 

If they are not making noise, you might still want to check them. Rock the shaft and watch / feel for play. I use a screw driver to try to force the joint either way to determine play.
My recommendation is "If it ain't broke, don't fix it".
Just $.02 worth.

 

It's a simple matter to remove the u bolts and lower the shaft , pop the caps off and check em. If they look good you can stuff some grease in the caps and reassemble. That will give you a good idea what the front one will look like.

 

Look around the caps for orange-red dust. If you don't see any, your u-joints likely are NOT running dry and likely do NOT warrant replacing.

FWIW, my Five-Seven Shaker, which I've had for 56 years, still retains its original u-joints. I don't plan to replace them until/unless it's necessary. I don't believe in making work for myself.