I was told by an 87 Allante owner that they 4100's in the Allante's were assembled by special technicians. You would have to go to the Allante club message board to find out.
The 91's and 92's have the 4.5, the vent windows, the Recarro seats, and no Northstar complications, although the guys with the 93's think that that is the ultimate, and look down on the 87-92 crowd.
Truthfully, they all have certain inherent problems, but if you get a good one, decent miles, only 1 or 2 owners, it can be relatively trouble free.
I have a super nice 92, pearl white, with a hardtop, 105K miles, completely serviced, chromed stock wheels, brand new Goodyear eagles, really a nice car, that I may have to sell.
Hit my email link if interested in talking.
Thanks,
Brian