My first question is, how do you know the engine needs to be rebuilt? You say you don't know the "true" condition of the motor, then how do you "know" it needs to be rebuilt? You need to do a proper compression/leakdown test to determine the state of the rings and valve seats, and possibly pull the pan and check some bearing clearances to see how the bearings are doing.

 

The a/c lines may have to altered at the connection to the a/c core in the air box and the wiring from the a/c controls to tell the compressor to run but other than that I don't see why it wouldn't work. but to be safe i would just use the factory a/c compressor. the bracket should just bolt right up to the block condsidering it will be the same size if going from a 289 to a 5.0.

 

I should probably rephrased my thoughts. The Heads are well used and they "tick" for a while after startup. I would attribute this to a well worn CAM Shaft or the valves themselves.

My thoughts are if I am going to pull the heads and replace or rebuild I might as well go roller rocker and then replace the cam shaft. If I am going to replace the Cam shaft.....you can see where this is going. If I am going to do it I am going to do it right.