1983 Chevrolet C10 - Need help

[cLaWz]

Where to begin...

My fiance purchased a truck from her stepfather for $1,000. Used it at their ranch and around the small town she is from for a long awhile. Apparently at some point in time there was a fire under the hood with the original 350 so he tossed a 454 in it along with a replacement wiring harness.

To be honest, this truck is more trouble then it's worth in my opinion but my fiance has an attachment to it.

All started back with the distrubutor flaking out. Then I had a bad leak form at the transmission cooler connection into the radiator. On top of that it is leaking oil from the rear main seal I believe. A lot of other stuff going on but the symptoms below are our biggest problem.

Got hotter then normal the other day while we were moving to our new place (by maybe 20 to 25 degrees) and found the radiator was low. Topped it off and took it for another drive... started getting hot again as I pulled back into our driveway and it puked out over 2 gallons of coolant onto the driveway through the overflow container.

Only thing I have done so far is a quick visual inspection due to time constraints. Current plan is to pull the thermostat and test it, then move on to a pressure test on the radiator. Doing some research here on the forums I can let the system sit pressurized for 2 hours or so and at the completion of that pull the plugs then turn the motor over and watch for any coolant coming out. Should tell me if I have a head gasket problem. Guess the easiest check for the water pump would be to run it for a few minutes then check for circulation but I am not sure if it is wise with the way it is acting. Any suggestions on that front?

I'm a "weekend" mechanic per say. My ideal would be to find a used complete 350 from somewhere and do a swap since we *really* do not need the 454 and the 8 MPG that goes with it. Never done a full swap but I'm sure I could handle it with some time.

Anyone have any advise?

Thanks