Our 4 piston bracket design does not require you to tap or modify the knuckle. As far as I know we have not had our brackets confirmed by a customer to fit the R33 GTS-T, however we have had them run on R32 GTS-T. You may know a bit more than I do in regards to your front knuckles. Based on a quick search of the R33 front knuckle they look very similar to the R32.
That being said, I cannot confirm fitment for your particular application, but if you were to order a conversion bracket kit from us you would be need the S-Chassis version if your knuckle is cast steel. If your knuckle is cast aluminum you would need our Z32 conversion bracket kit.
The only thing that changes between the two kits is hardware length, due to the difference in material, the caliper mounting bosses are different thicknesses.
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