Most brands these days are good, but I'd recommend one with a double floor, and a 6man over a 4 even if you only fish with 4...more space is important when things go bad. As for install, most Grady hardtops cannot support the weight of the liferaft, I'd call Grady and find out. Personally, I'd spend a few extra bucks and buy a valise, it takes up less space. Buy a light one so your crew(wife, kids, etc) can lift it.
The one Scarlet Knight purchased would be a very good raft, revere is a good brand also. Viking would be my top pick if it is a hard canister, but they are typically heavier and harder to mount and store. You could place it in your walk around up forward between the anchor locker and cabin. I have a 6 man canister that I tie down on my bow in that area, but at 80lbs, you feel the weight of it that far forward. As soon as it needs a repack, I'll buy a valise, but the one I use I did not pay for so I was not going to say no and not sue it.