Since I finally got the all hose clamps I needed from the salvage yard, I was able to install the heater hose connectors. I definitely wanted this to be done before the engine was back in.
3/4" heater core connectors and 1/2" rear heater core connectors. The hoses to the two nipples on the water pump are 5/8":
About 12" each of 3/4" and 1/2" heater hoses and box of 3-way Ts and factory hose clamps (factory from GM, Ford and Honda

)
Semi-comfy seat on cross member in engine bay:
The 1/2" tubes were too close, so I trimmed them down:
Minimal, but adequate gap and perfect alignment:
