How can you tell buy the engine serial numbers if they are the Bulldogs or stock 500's???? Thanks

You have to run the serial numbers through a merc database. Post them and somebody may be able to help you out or just have your local dealer run the serial #.

Bulldogs are tall deck blocks (10.2"), hp500 are standard blocks (9.8"). Look at boss where water pump attaches to block, tall deck block has an extra block between deck and boss (0.4"). Short deck doesn't, boss meets deck surface.

I think the BULLDOG is a bowtie block and has an extra oiling screw on the front of the block ,,,a little allan plug is in it ,,its about 1 inch from ceneter in front of the block above the timing cover !!

Thanks Guys