Today’s A body work. Love this car!

New rubber will feel very good, poly will feel everything. For a driver I'd go stock new rubber. Air shocks on an A are just a crutch for weak springs. New shocks alone are not going to affect your ride height. Shackles are cheap if you cant afford new springs yet to get your tail out of the mud. Make sure your disk brake conversion uses your spindles (many are made for 9" spindles) and can accept your current wheels. I don't think and 13's fit any disks.