Assuming you don't have any pin holes, loose rivets or bends on the wheels to leak air, the smoothness of the rim beads and smoothness around the valve stem hole will be the areas to leak air. Clean the areas well and/or paint or powder coat them. Be sure to carefully inspect the wheels before painting or powder coating them to make sure they are safe. You don 't want to cover up cracks, bad rust or badly rusted rivets so you can't see them. It is also very important to install a tire with an appropriate recommended minimum wheel width. Measure the wheel dimension from inside bead face to inside bead face to determine your wheel width then compare to the tire you are considering and discuss it with your tire dealer. Many older Chevy wheels are 4", 4.5" and 5" widths. I run 215/75 16 LT 8 ply rated tires (minimum recommended wheel width 5.5")on my 1954 Chevy truck rims. I'm on my fourth set and know several people who run the same size. I don't know the recommended wheel width for 225/75 tires. I am not a tire expert so rely on your tire dealer for safe application.
