A/C and cooling problems

I bought a 92 LSE in February of this year. The a/c was inop, and I didnt' worry about it until things started heating up around here. Also, the truck has no heater core. Anyway, I put the new compressor on, which works beautifully, but now the truck is overheating. My mechanic initiallly thought it was not holding compression and suggested a new reservoir cap, as the old one was looking a little worse for wear. I got that and it still overheated. This time, I noticed the water pump seemed to be emitting steam. I had a new pump shipped to me and put it on. The thing still overheats. The thermostat is open as you can clearly see the coolant moving around. He tried to do a compression test, however, his unit would not get a good seal and he was really tightening it onto the reservoir. Also, the top radiator hose was hard as a rock and hot, hot, hot! Interestingly enough, the lower portion of the radiator is cool to the touch, but the top end is rather warm. Maybe the radiator is plugged up. My mechanic stated it could be head gasket time, but also opines that it may be the rings are bad, as there is blowby at the dipstick and crank shaft filter point. He suggests a new engine, verses a rebuild.

I have read some of the posts on overheating, but did not glean any solutions there. I guess the new a/c compressor pushed an already weak cooling system over the brink. I love the truck and will do what it takes to get it fixed. I've got 134K on mine. It had 129K on it when I bought it and it drove fine until putting the a/c compressor on. By the way, the a/c is ice cold.

I am open to suggestions.