Would there be any harm using a donut on my 1972 cutlass cvt? I could use the trunk space and cut down on the weight I'm hauling around. Currently I have stock 14" wheel and tires. It's a weekend cruiser so if I got a flat I wouldnt have to go far and help is a cell phone call away.

 

As long as it has the correct wieght rating and you didn't drive far on it.

 

I opted to keep my full sizer as "trip interuption insurance" as I drive mine long distances. If close to home, then a donut can work.
Keeping a small air compressor and a plug kit could be beneficial also...

 

I would keep a fullsize ready to use spare, if you have a puncture you can put it on and carry on as normal.
If you are going to a show or cruise your car will look out of place, and how much trunk space will you free up?. You will save a little weight, but unless you are at the strip I doubt you would notice.
I had a tire failure at a show recently, I didn't enjoy the 80 mile trip home at 50 mph on the space saver spare, and I had to find room in the trunk for the road wheel anyway.

X2 on keeping a compresser and emergency tool kit in the car as well.

Roger.