[mrein3]

You're dealing with WAY too many variables here. This is what I would do in your situation.

#1 I'd get the proper shroud and a 7-blade factory fan and new fan clutch.
#2 I'd run a 192 degree thermostat.
#3 I'd change out that thermostat and burp the system. I would not start that engine again until I'm burping it with #1 and #2 complete.

To burp it fill the radiator to the brim, leave the cap off, put a catch pan under the cap area of the truck and start it. As the truck warms up you'll notice flow then no flow as cold antifreeze from the radiator is exchanged with hot from the engine. When you notice a good, constant flow, top it off and put the cap on.

The system is now burped - you removed all the air from the coolant system.

NOW if you overheat you need to worry because except for a new radiator, your truck is now functioning on the coolant front the way the General intended it to.

Let us know what it is doing after you get the right parts on there.