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I have only had about a handful of people ask me for a '90 rebuild kit so it hasn't been worth my time or effort. The seals are different as is most of the hardware than the '91-'99 kit. I had someone try it out years ago and they were not able to use most of the pieces. Your best bet would be to take the throttle body apart and take the hardware to your local shop and have them help you match it with some nice stainless steel allen head bolts. The '90 seal sizes, and probably Chicago Rawhide part numbers, are probably posted on here so a little bit of searching should produce that information. Then just find a place online to order them.
In looking at the GVR4 throttle body, it looks different than the 1g/2g throttle body and I'm going to guess the hardware will probably not work. I haven't been able to confirm yet if the shaft seals will work as I can't seem to find size information. Are you still running the factory throttle body, and if so, can you post up a couple pictures to confirm that it is different?