Need some advice

[Rusteeze64GB]

Here is the story. Bought my 1964 GMC custom cab 3/4 ton fleetside for 950.00. The truck had no glass, interior was painted, exterior was prepped but never painted ended up with rust. There is light rust on the undercarriage. I have been working on that. My concern is the engine. I was told the truck drove 4 years ago but, then I was told that the hood was off the engine for a while. I sent the carb off for a rebuild and the carb guys told me that the carb had water damage. I bumped the engine a little bit tapping a screwdriver on the starter and the crank was only turning not even a 1/4 turn. the water pump is shot and altenator too. I was going to start really tearing into the engine this weekend. I want to keep the straight 6 that is in it. However, I am afriad that the engine might be shot. I have looked around for another used 230 and it is looking like I will spend $300.00 for a decent one. Honest opinion, should I rebuild the one that is in there or buy a new one. Just to have the head rebuilt at a local machine shop they quoted me $150-$200. Opinion's needed. Thanks! If there is anyone in the Phoenix area looking to get rid of a striaght 6 for cheap, I am interested. Thanks in advance for the opinion's.