What kinds of problems are you having with the old girl? Have you done a compression check?
Mine is a vintage 1975, but it was rebuilt in 1994. I've since replaced the head gasket and the carb, among other smaller fixes. If you have a modicum of mechanical ability, they are easy engines to work on, assuming you have decent access.
Tell us more of your story.
Also stop over at the Moyer Marine site at Moyer Marine Atomic 4 Engine Rebuilding and Parts
. It's a specialized forum for the A4 as well as a great site to get parts. A wealth of knowledge over there, there is!