It sounds like you need more radiator. I drove and worked a D200 pickup for many years. The stock radiator was just big enough. When it started heating up loaded on long hills I knew it was time to rod out the radiator or replace it. That always worked.

A bigger fan won't help you. I'd find a good radiator shop, pull the radiator and have them look at it. If the prce is reasonable, have them replace the core, preferably with a thicker one (3 rows instead of 2 for example).

The other option is to buy a new high capacity radiator. I've had good results with the stock style aluminum radiator from Mancini. Its not the cheapest (nor the most expensive) but works well. Mancini will work with you to get the right size, outlets configuration, shroud, trans cooler ect. Stock replacement hoses fit on mine which is a benefit.