If I recall correctly (and I know that could be a long shot) the 1990 Iroc would have come with Goodyear Eagle GS-C's. I have a 1990 vert with just under 19,000 original miles and a set of these tires that have half tread or more left. The last number of the DOT code is a 9, meaning they could have been made in either 1989, 99 or 2009. I know for a fact they have been on the car for a while due to the age cracking in them. Just wondering is there any way to know whether they are the original equipment tires or not? I am going to replace them, but if I think they could be the ones that came on it new I might just keep them in the garage attic for the hell of it. Thanks in advance for any help or advice. Scott.

I'd put money on it that they are original, especially with mileage that low. They are the correct tire that was used.
I'm the 2nd owner of my ride and she still had the original tires on her when I bought her in '99 with 27,600 miles on it. In '03 at ~40,000 miles I replaced them with the exact tire, still available at the time from my local Chev dealer.
So today, my ride is only on it's 2nd set of tires, EVER! And they are still the correct OEM type. Tire condition is still good with 75% tread left, never stored outside, and up on blocks when winterized to prevent flatspotting or floor contact.

Not sure if they are still available today, but they had them on the rack (as well at TireRack.com) as little as 5 years ago.

my 90 came with goodyear eagle - there is a pic of it taken a few years later but i always bought stock tires until i started playing with it.
i cant read the 3 other numbers on the car pic.
maybe you can.
but i have owned that one sice 90 when i bought it new.
nut its not an iroc/z28.
it would have had to have been built in 89 becasue in 90 chevy lost the iroc lable and it became a z28 again.
only those made in the early part of the 90 year - started in oct 89 - would still be an iroc. i may be off a month or two.

They probably were off of a '99 F-body, they had the GS-C tires. Those weren't introduced until '93 when the 4th gens came out.

Original tires would be the Gatorback either VR50 or ZR50

Didn't the fourth gens use 253/55/16?

Goodyear eagles were standard..GSC's didnt even come out until years later.
and 4th gen 16x8's came with 245/50/16

Correct, my '87 has 245/50/16 and my '98 has the same size tire.

2.73 geared Z28/TA's got Goodyear GA's in 235/55/16. If you got a Z28 or TA with 3.23 gears, you got 245/50/16 Goodyear GSC's. That was in '93.

Goodyear Gatorbacks were on 3rd gens.

I agree with the others about the gatorbacks, at least for cars that came with the 245/50-16 tires. My understanding is that they were VRs until sometime in 1989, when they switched to ZRs.

My '92 had Goodyear ZR gatorbacks factory. I still have them in storage.

Clear as mud.