On 1968 C10 heater core which tube comes out the top of the heater box?

[HeavyHauler]

I am getting ready to put a new heater core into my freshly restored heater box for my 1968 Chevy C10 396 big block short bed fleetside.

Which tube should be coming out of the top of the heater box and which should be at the bottom?

My truck is heater only from the factory.

In the pic I provided does the smaller outlet hose end at the top go to the intake manifold while the larger outlet hose end at the bottom of the pic go to the water pump?