Heater core outlet diameter

What size of bosses do you have on you engine manifold and pump that pumps water to the heater core? My 70 SB plumping is 1/2 pipe nipple intake manifold / (1/2)hose to heater core, 5/8 hose from heater core to 5/8 nipple on the water pump. Heated water to the heater core is almost always the smaller hose from the manifold. 3/4? No never heard of this. If you got to, you can hardware this...take your old fitting off of manifold, ask the man at hardware store for this size pipe to a 3/4 nipple, for you 3/4 hose to you heater core. This is an option. (?)