I thought I had lucked out as there is a recent receipt from a known Volvo indie shop for the dash blower replacement not too long ago, until I pulled the heater hose off the block the other day and saw the fitting was so full of rust packed solid a #2 pencil would hardly go through it. :(
The radiator has been replaced very recently, now I know why. What I can see of the block coolant passages actually looks alright, but that fitting, the hose end of the hardline, and the firewall fitting to the heater core were pretty rough with rust. I assume the odds are good I'll be putting in a heater core soon?
How bad are the cheap one's? My 83 with the stock heater system has almost comically good heat for N.C. winters, way overkill for weather in the mid to upper 20's at worst. For the money I'm tempted to get one of the cheap one side in-one side out cores.

When the motor's back in and car will move I'll flush the system and see what it does I guess. Anything else to be done? Should I pull the heater control valve, that I believe is original style, off and clean it?