Replaced thermostat and water pump engine temperature starts to climb after 6 or 7 miles a/c cools but heater only gets warm

engine temperature starts to climb after 6 or 7 miles
Climbs? Does the coolant boil over or the engine overheat, i.e.: temp goes into the HOT range or check gauges message, anything?
What are the ambient conditions when your truck does this?

a/c cools but heater only gets warm
You could have a partially clogged heater core. If you can't verify coolant flow, I'd consider replacing the heater core for this concern.