The swap you are proposing isn't too difficult. Following is what you should consider:
- the clamp ring for the rubber diaphragm
on the old 120S and the new clamp ring for the 130S will interchange on the old bed
, so that's good..
- occasionally a hull
has a "deep V" configuration where the saildrive leg protrudes from the hull
, and that requires a saildrive leg extension to get the propshaft far enough down to have correct prop tip clearance. The old 120S had extensions available, but the new 130s doesn't, but it is about 25 mm longer. With a 1990 vintage hull (fairly flat in the stern) I don't think this will be a problem for you.
- You are correct in your assessment of the need for spacer blocks for the front engine
mounts. The D2-40 block is a bit longer than the 2003T block and the mounts are slightly higher so you will need to fabricate blocks to bolt to the bed for the new front mounts to sit on. These don't have to be steel
....aluminum will do.
I have drawings of these blocks that you can use to fabricate from, but I currently am in FL, and the drawings are at my home in Chesapeake,VA. I won't
be able to source them for about three and a half weeks. If you can wait that long, I'll be happy to help you. Otherwise you might be able to find the required drawing info online.