if you find anything else out let me know but here's my 2 cents.
I had an old 440 hull and was going to drop a 650 it it. (I'm not sure how similar the 650s and 750s are, 650s are the newest stuff I fool with.) The rubber coupler between the crank and the pump shaft is the same on 440s 550s 650s (and hopefully 750s) To make the 650 fit, you have to adapt the motor mount plate to be able to attach the 650 block and get it to line up with the coupler. which meant lowering it about 1/4 or 1/2 an inch or so if I remember correctly. You can get your exhaust setup to work pretty easily I think with some flex radiator hoses from Auto Zone or something. You may have to swap ignition boxes but the 550 box should be able to run the 750 if you get it hooked up correctly.
That project ceased when I was given a 550 to drop in so I put that in instead. No modifications. I still have dreams of a 650 or 750 powered 1st gen ski.
Hi, I`m going to put a 650 engine in a 550 hull,
you need a adapter plate for the conversion, it cost 89,90
the 650 is similair to the 750 ( same motor mount plate) eBay... m330255764807
I`ve got an 750 engine as well that I maybe going to put
in the 550 hull later, as far as I could see the stock 750
exhaust won`t fit in the 550 hull, but I`m not sure?
I never knew you could get an adapter plate. That would make life a lot easier. I thought I was going to have to fab one up or frankenstein an old one. I know almost nothing about 750s but from a couple pictures I find, it looks like if the expansion chamber will fit width-wise into the 550 hull, you should be able to make the rest work.
Sounds like fun. My dreams of a sleeper 440 are coming back to life.