Yep I agree probably way to much work. Unless you are badly under powered I would fix of replace in kind. If you have really good access and you are willing to put in a new motor base you certainly can do it.
I replaced my motor base a couple of years ago, I have a 2GM. Not really a bad job, cut out the old unit, grind down the tabbing and then re-install a new base made out of plywood. Glass it to the hull and do an alignment.
It can be done but in my case I had the pattern, you would have to design the base your self so that you had the right height and angle to your shaft. Then fuel lines, throttle controls etc are likely to be different.