Hi David,
Most parts you will need to refurb. are easy to get. Here are a few sources:
http://www.vintageoutboard.com
http://www.marineengine.com both ship out of Washington state. The Sierra coils are as good as or maybe even better than the OMC ones and available at your local NAPA store. Best to stick to OMC brand for the impeller though. There have been some problems with the Sierra ones. Those things are likely all you will need for a refurb. Many in the AOMCI just clean up the points, and go through the carb without getting the kits because they feel the new parts are quite lacking in quality compared to the originals. Small carb parts can be had from marineengine.com so no real need for the kit.
Try to get one with the lower cowls complete, especially the Johnson as the the front carry handle pieces cost a fortune if they are broken or missing. Johnson and Evinrude are identical except for the fuel tank mounting and cowls.
Try to find out what mix it has been run on, 16:1 is the design mix as it has sleeve bearings, 24:1 probably acceptable.
The compression should tell the story there. I would not discount one with 70 lbs. compression as you can usually gain 5-7 lbs compression by truing the head and deck and installing a new head gasket ( breaking head bolts is a danger ) but one does get experience drilling out broken head bolts that way.
Should not be a problem with deeper immersion, the water circulation telltale is a fine spray of water about halfway up the tower. Well maybe starting not sure about that, no problem once running though. Running in a strong following swell with a sailboat it ran fine with water up to the top of the tower and alternately throwing the prop out of the water at the top of the swell. Could have used a long shaft that day!
I have about a dozen of these motors that is how much I like them! Need more info let me know.