I may be wrong, but I thought vents either side of the cluster was indicative of 'factory' air.
I can't see enough of the heater box through the engine to really confirm it.
Honestly, I own a Bricknose, so a lot of the minuteae is lost on me.
I just try and adsorb as much as I can.
Now
under the skin, my truck is much more '80-'86 than '87-'91
Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.