Gimbal ring bushings worn???? Noise only coming from outside????? Spray a little WD 40 on each and try to work in oil. If noise is reduced, then replace bushings. At least you will know if noise is coming from them.
If v8s were pulled there is a chance that some rear motor mount parts may have been dislodged and fell in bilge. Happened to me too. If it does, you will never align anything.
A number of headaches may await you. Pulling drive and manually inspecting bearings and u-joints is a must. But, that's an old boat and may have ROT in transom or stringers which will cause motor to shake when under a load. MC's engine mounts are strong. Closely examine motor while someone else...
I don't put much faith in Mercathode. However, I don't leavy my boat in salt water. They will suck a battery down if you don't have shore power and good battery charger. I have a Bravo 1 and my zinks look like yours.
That old of a boat, I believe it is time to pull drive and replace all hoses and bellows, at least look for cracks. 10 years is about average life here in NW Florida.