LS Timing belt ONLY works with LS WATER PUMP
B16 Timing Belt ONLY WORKS WITH B16 WATER PUMP
GSR/ITR Timing Belt ONLY WORKS WITH GSR/ITR WATER PUMP

Im 99% sure the B16 Water Pump is the same as the ITR/GSR so the WATER PUMP is interchangeable, ovviously not the belt.

The LS has like 22 Teeth on the Water Pump and GSR/ITR has 19Teeth.

Belts are slightly different too IIRC