The 87-88 timing cover was flat at the bottom where it met the oil pan. The 3.4 also used the same timing cover gasket as the 87-88.
The 87-88 was flat at the corners but the pan had a "scoop" cut out of it. The timing cover had a rounded section where the crank nose came through. This was essentially the same as the Chevy V8. And the 3.4 did use the same style pan and gasket.
Timing covers were interchangeable across the 2.8, 3.1, and 3.4
if the matching oil pan was used, and
if the correct water pump orientation is observed.
This is the 85-86 pan gasket.
The tapered area to the left is what seals the "45 degree" nose of the pan. The black seal goes at the rear, around the crank.
This is the 87-88 pan gasket.
This is the correct WP gasket for our cars. Note the rectangular port on the right.
This is the gasket for the "other" water pump rotation.
I hope Rockauto doesn't mind the hot-linking of their photos.
