in the area you live with no crime control you need a smashed up vehicle that fits into the location. the nova sticks out and becomes a target.
the nova you have is not going to get a new drum. to change over to disc which is what Nova owners do , you will require both front and rear conversion to disc brakes. it will cost a good amount. after you fix it it will end up in mexico.
work the drums with penitrating oil [not wd-40] .. then replace the shoes and see how it goes. best do the front shoes also.
I did find drums for the 64-74 nova. bd-2045 5 hole drum 9.5 dia.