Your tranny is...
There's a good chance your '83 Regal came stock with a 350C. My '81 Monte and '80 p'up had this setup. The C means convertor lockup. Look for a two-wire, weather pack connector hanging loose from the firewall.
If you now have no lockup, the tranny has probably been replaced with the tried and true 350 (what I did to my Monte and p'up). Basically the same thing without a lockup.
Bry593