[trooper Tdiesel]

at least in my area, its very common for trucks 1/2, 3/4 or 1 ton to be changed over to the 285/75/16 size as people do it to "fill the wheel well up, to make the auto look better" and on many 1/2 ton trucks its the biggest size that can be jammed on without a lift kit of some kind.
the one i drove one time, compared to are truck. it was very different in drag off the line, but that was comparing a new set of 285's mudder's with a full 17/32s of tred. to a ten~ year old 235/85 road tire set with about 8/32s or so.

265/75/16 is stock, for your truck, being a silverado..
a low end or fleet model would likly be smaller 15" as i know someone with a 2wd with the 4.3L what has 15" rims from about 92/94 year
any way, the original size will be on the drivers door frame unless the truck was repainted or maybe the door was replaced for some reason.
but there are two other sizes that are very close to the same height. 235/85/16LT is nearly dead on.
and the 215/85/16LT is a little shorter, it would be better for lots of city driving with little to no steady at speed driving
but they are known for having a harsh ride as there stock sizes for 3/4, 1tons in the 80s/90s and have high load ratings


you would have to find a different set of rims but....
for around town, another option is to go to 15" with a 30X9.50X15 versus a 265/75 at about 31.6"
there also available in a P passenger tire type that would lower drag and be the best around town tire for having the least drag you could put on the truck short of a smaller 235 or 215/75/15, and be about $30 ish a tire less then a LT light truck tire of the same size..
but if you move more then about 500lbs or so in cargo in the bed, or spend any real time on rock roads at speed, id advise the use of the LT tires as thats what there made for...