The upper rad hose doesn't get full usually on your year truck.
It is often higher than the rad cap so it keeps some air in it,what you really want is all the air out of the engine below the thermostat.

The best you can do to get totally full is to jack up the passenger side so the rad cap is the very highest point in the cooling system,run the engine till the stat opoens and increase the running rpm to about 1500.
Fill the rad to full and cap it,then let everything back down-the system will push out what it doesn't have room for while running and if the cap and overflow system work properly,it will suck the same amount back in when it cools.

 

That leads to another question: Why don't they have the radiator cap directly on the radiator? My pressure cap is on the overflow tank. I would think having air in the system anywhere would allow for those hot spots to develop since the air will compress and not necessarily force the coolant into the smaller nooks and crannies.

 

Ok my mistake,I thought 94's were on the rad rather than the surge tank.

Since it is a closed system it doesn't much matter where the rad cap is.

The pressure the system builds is what forces the coolant in,and air will always try to rise to the highest point.

 

racer,

I was checking out a 17 page thread on DP that you were posting in and another person had the same issues as me with the fluctuating temps. They put in a 12559338 thermostat and cured their problem. I ordered one from my local parts place today so I can put it in. I will post back once I have had a chance to see how it works.