I flushed the system and put in a new 185 F thermostat. For the lower heater hose, the hose specified for a '66 fit, though I did have to cut about 6" off of it. It is a Gates part 20345, a good American based company. For the upper I had to use a Gates 18" flexi. One hose was made in USA the other in Mexico.
Tridon brand hose clamps, made here in Tennessee, were available at Home Depot. Stainless Steel no less.
This thread helps with hose routing:
http://www.67-72chevytrucks.com/vboa...r+hose+routing
I got it all together and....no heat.
I'll save the full dialog, as that was discussed in this thread:
http://www.67-72chevytrucks.com/vboa...d.php?t=608492
But the punchline is I routed the input hose off of the top of the thermostat housing, not the intake.
Once I got the input hose to the right place, I burped the core by loosening the intake hose at the core and pulled it almost all the way back. Started the engine (cold so as not to spill hot coolant) pulled the hose off for a second until there was a steady flow, and popped it back on. If you do this hot you can get burned.
Now the heat is smoking hot. I remember now why back in high school I never bothered to fix the broken fan motor on my first truck...