heat barely works, used to have a/c. help needed.

If it's like any other backyard AC removal, you mean everything from the firewall forward got yanked and trashed.

Factory AC cars use a water valve mounted on the passenger fender apron. The original ones get frozen in one position over time and then you get barely any heat or heat even when you don't want it.

Check that first. No luck there, check the stat. No change there, then possibly the heater core is plugged. You can back flush them with a garden hose and moderate pressure.