Lower Unit/ Complete unit? Which Gear Ratio?

[Colt45W]

Hello,
I just got a 1992 Cobalt 223 with the 5.7L Mercruiser Alpha one Gen2 Combo for free and am looking for some advice and help. The previous owners had taken it into a shop after years of neglect and sitting in a lake. They ran the boat a few months ago and were cruising at 45 before taking it in for an oil change/tuneup. The shop discovered that the lower units bearing carrier had corroded to the point that one of the seals was completely gone and that had allowed water into the unit. The shop recommended a lower unit change at the minimum and a full unit replacement preferred. I would like to put as little money into the boat as possible but I also don't want to just replace the lower unit to have the upper fail me this summer on the water. I was considering just replacing the bearing carrier assembly but the lower unit itself is in a pretty bad state of corrosion as well.
So I'm looking for advice on what to do. I drained the gear lube and there was very little milky color and rust color inside, but I'm thinking the shop it was at had just put in that gear lube since it looked so good. Attached you will see some photos of the situation. Any suggestions and/or help on choosing which of your drives is the appropriate replacement would be appreciated.
IMG_1868.jpgIMG_1852.jpgIMG_1851.jpgIMG_1850.jpg

[Technical Support]

Hello. Looking at these pictures, it does look like you need a complete replacement. This is some very bad corrosion which I suspect is caused by electrolysis. The boat may have been kept in the water at a marina and an electrical source close by caused this heavy corrosion. I would recommend calling us to get a quote on a complete replacement for your boat. This would be the best course in case water did get into the drives and started rusting on the bearings and gears.