Mercruiser to Volvo IO question

[bigeasy1]

I may have a chance to pick up a 3 year old 5.7 MPI Volvo Penta engine and outdrive for a 74 Tsunami that i'm restoring.My original plan was to install a new 300hp 5.7 MPI Mercruiser with a bravo drive,but i might be able to get the Volvo for something like $5,000,it has 150 hours on it.The new Mercruiser will run me in the neighborhood of $11,000 to $12,000 bucks,give or take.
The other advantage is the volvo is in a boat,with a decent trailer,so i may be able to use the gauges,steering etc,and be able to sell the trailer and boat,even for a give away price to make it even less costly.
Will the Volvo outdrive be a big problem covering up the old transom cutout,which was a early version mercruiser alpha.I'm redoing the transom from the inside,and am about halfway done.We're laying up a couple layers of 1708 to the inside of the of the outside skin,then marine ply,and new inside skin.
The dealer i spoke to said to leave the cutout on the outside of the transom,as he would use that as a guide to cut through the new ply for the outdrive.
For those of you that did transoms from the inside,did you also glass over the outside cutout?Wouldn't different drives require different size/shape cutouts?
Sorry for all the questions,but any info is appreciated.

Thanks J.R.