Hi Mootspoints,
Based on a quick image search your boat has an MC-1 or R drive (many people call these "Pre-Alpha"), this was what came with the Mercruiser 898 or 228 package. I believe in 1980 the Alpha One came out, any Alpha One Gen One drive will mount to your gimbal no problem.
As far as the loose steering is concerned, that would require a replacement of the gimbal ring, originally mercury used a spline steering shaft, but later changed the design to a square shaft because the splines were not able to be adjusted and would wear out much quicker...
Hope that helps some.
-Andrew