Hope you are enjoying your 'jack hammer' diesel while we enjoy the quiet purring of our A4's! :g
If your boat is from 1980 then chances are your engine is a 'late' model engine as Universal stopped making them around 1983 but you can't rule out someone swapping an older working motor for a dead motor.
The dipstick on both types of engines is located near the back of the engine as it is usually tilted down at that business end in both direct drive and 'V' drive applications.
The stuff that is 'early' vs. 'late' model engines capn_dave gave you a very concise review of.
I would look for the serial number as capn_dave describes to figure out if the engine block is 'early' or 'late' model, but with a boat made in 1980 I'd bet on 'late' model engine block.
Other components may vary. An 'early' model carb could be fitted to a 'late' model engine and a 'late' model carb can be attached to an 'early model one. Most A4 installations I've seen do not have an oil filter as a rule but you can add one if you like but this gives no indication as to 'early' or 'late' model.
As capn_dave outlined, the most important part of figuring out the 'early' vs. 'late' model stuff is:
1) distributor: Delco or Prestolite?
2) thermostat housing on head near flywheel: present or not?
3) carburetor: aluminum (5 screws hold it together) vs. cast iron (4 screws)
4) transmission cover: rectangular or 'tomb stone' shaped
Here is a 360 degree photo of a 'late' model engine as refinished by Moyer Marine: MoyerMarine
Other engine components that may vary are:
- fresh water cooled (FWC) or raw water cooled (RWC),
- one water pump required for RWC, two for FWC
- electric or mechanical fuel pump.
The best resource I have found for the A4 is here: Moyer Marine Atomic 4 Community - Home of the Afourians - Powered by vBulletin
Everybody likes pictures so post a picture of your A4 if you can.