Radiator is out, what can I do in the meantime?

Phreakish said
Definitely not a bad idea to flush it out and take a peek at the thermostat.

I once had an issue with the heater not being very warm and the engine temperature would surge (from 180 to 210 back to 180 about every 15 seconds). I back-flushed the heater core and got a ton of gunk. Then hooked up a couple hoses and held them pointed skyward while I filled the core with a radiator cleaner. Back flushed it and got a ton more gunk out. The heater never worked so well before!

Short story long, since you've got the system empty, it's probably best to flush and inspect while you can.

I agree flushing is well worthwhile!!! one thing I have noticed with all my slant cars is the neck ( that the upper rad hose goes to, they originals are alum and all had pinholes in them. I ordered new ones, from ROCK AUTO, PRETTY CHEAP, AND MADE OF CAST IRON. ( who hit the f riggin caps? not me!)
I would replace the upper and lower hoses , heater hoses, unless pretty new, fan belt, like he said, the water pump..
for those guys that always want to replace the slant, maybe they would donate us some $$$$! LOL
actually, I keep being amazed at the number of people (inc me), that find joy with the thing!!!! O K so I have some cars with BIGGER engines for when I feel the neeed for speed.