[hotrod_chevyz]

Sounds like it needs a heater core and a tune-up.

Start simple, Fuel/air/oil filters, oil and spark plug change, new plug wires ect. Do a visual inpection and see if any vac. hoses are misrouted or broken/cracked.

Its not good to breathe in the antifreeze vapors. You should at least bypass or replace the heater core.

Watch and make sure the oil pressure isnt dropping while its hot, and watch and make sure its not running too hot.