The size tires that are on a 1992 Chevy Silverado 1500 are 235/75R15 tires.
I have a 1992 Chevy Silverado 1500 and my front and back tires are all 235/75R15 size tires.
Although some models such as the 454 SS, uses 275/60R15 tires.
The specific tire size can also vary by the trim level such as Cheyenne etc.
But 1992 Chevy Silverados use 235/75R15 tires.
225/75R15 is another common tire size for the Cheyenne trim models.
I use Nexen tires on my 1992 Chevy Silverado 1500 although I used to use GoodYear Wrangler tires but I found that the Goodyear Wrangle tires start cracking sooner than the Nexen tires so now I use Nexen tires.