Thanks - I'll check the fan belt - thats an easy possible fix. It has also been suggested to me the water pump may be squeaking as well having been stored dry for a few years.
Engine is running Edelbrock ali heads with roller rockers, and has been run previously on a Dyno about 4 years ago.
I had already primed the engine with a drill down the distributor hole and seen
oil coming up to the top of the engine on rockers, and as its a re-built engine galleries ought to be clean.