TOPIC: Going from 2-stroke to 4-stroke

With my Dorsett Catalina project on hold while I'm in Alaska for the summer I've been pondering power options. I'm not interested in a period-correct power plant (this is a functional restoration), and I plan to put a modern 4-stroke on in a few years. In the meantime I have three engines to choose from to rebuild and hang on the transom. My preference will be for the 1993 Johnson 48 Spl, but I won't know it's condition until I tear into it this winter.

Anyway, my plan for the boat is to have a pair of custom aluminum talks welded up to fit on each side of the boat. I'm curious if I will have any problems if I run the tanks with mixed 2-stroke fuel for a couple years and then convert to 4-stroke power later. Will the conversion be as simple as draining all the mixed fuel and topping them up with straight gas? Would I be better off running the 2-stroke engine off of portable tanks and saving the new aluminum tanks for when I get the 4-stroke engine?

Any thoughts?

This, and no problem. Some oil in a 4S won't hurt anything..

Will the conversion be as simple as draining all the mixed fuel and topping them up with straight gas?