I've owned 4 suburbans 72, 77, 84, and a 93 (all 4wd). My 93 was just stolen. I have been shopping for a replacement suburban. I've been calling people, buying trucktraders, newspapers, going on test drives, checking on line classifieds, tranderonline , etc. These past 3 weeks have reinforced my opinion that the suburban has never, ever been offered from the factory to the public in a 454 4 wheel drive configuration UNTIL 1992 with IFS.
Now to the issue of power, the 72 - I put a built 383 in carburated, the 84 was ordered from the factory by me (tried to get a 454) with a 350 carburated. The 77 had a 400 sb which we bought a reman 400sb and put a 350 TBI system on it (we still own this one - it's my older sons)along with a rebuilt 700r4. The 93 was a 454 TBI (with 4L80E).
As you might expect the power rating was lowest to highest: 84 350 carb ( heavy smog crap),
then surprising to me the built 383 carb is beat out by the 400 with TBI,
on top is the 454 TBI.
I also currently own a 6.2L diesel NA and for comparison it definately beats the 84 carb with smog, in get up and go.