Alright.. Where to start. I'll just sound off on stuff as I go along..
First let me start off by saying that when your looking at that pic of the L36 F-body LIM your looking at an awkward cross section of the runner itself.
The ports appear much larger but really aren’t.
1 thing I noticed between my buddy’* f-body lim and mine was the ports to the heads seemed much cleaner. There wasn't as much to clean up in order to gasket match..
The top half of this LIM (there are 2 one with an angled TB neck and 1 with a straight) makes up the top half of the runner.
The runners are much shorter than that of the fwd L36. And inside of the plenum, the entrances to the runners are bell mouthed. The length of the runners in the f-body is very similar to that of an fwd combo but with the HVII replacing the upper portion of the runners found in the UIM. I did measure at one point but I would have to really dig for the numbers.
Apparently these manifolds were both rated the same hp/tq stock as the fwd. So it may not make much of a change..
Many have installed this manifold for turbo applications. Essentially this isn't very difficult but the TB points toward the battery. (I installed the lower on a friends soon to be turbo regal so far)
Wizbang on clubgp also installed this but flipped it to the TB was facing the stock location. This took a good amount of adapting and fabrication.
There is also WickEdSix98 on fullthrottlev6 who modified the TB in order to get more flow. He’* with abbot racing and has dynoed 270 something n/a with a gyhugic cam and long tube headers.
The pics aren't there anymore though..
Injector location is the same at with the fwd l36 but one of the studs are in a different location.
I've also thought that the shorter runner in the f-body would be more suited since the engine could be attached to a manual trans, revved to ones desire, and IIRC they also weigh less. Basically low end torque isn't as much of a concern.
That’* all I can really think of now.