Starting with the crack in the 95 LIM. This was likely the death of the car. Note in the pics farther down that one of the ECT sensors was removed and a plug inserted. This MIGHT be a Riviera only thing, as this was originally from a 95 Buick Riviera:
On to the design differences.......
92 (very similar to 93):
Pic showing that both ECT sensor locations are identical:
Note in this pic that the 95 Riviera manifold has one ECT sensor removed and plugged, but the thread pattern and location are identical to all 4 manifolds I currrently have here.
Runner length isn't much of an issue on a Supercharged motor, particularly when you're talking the diffeence between 2" or 3". Not a significant change. The net effect of the 'chambering' on the 95 manifold could be negative or positive on horsepower and/or torque depending on how the air reacts in the manifold. My personal preference would be to have the spaces between the ports on the 95 manifold SOLID. Close the door in a sense so the air would be forced to go to the ports rather than eddy around.
Now I'd really love to see a 94 manifold. I have all the other bases covered. I'd also like a couple 94 L67'* to read the part number on the LIM below the nosedrive of the SC and post it here. It may be easier to read with a little bit of water smeared on it.