OK - You can use a TR/TS throttle body as it is the same diameter and bolts on but also allows for a much larger diameter hose and pipe to be attached as opposed to the VR-4 which has a fixed elbow which is smaller. As for the idle switch, swapping over a four pin TPS from a TR/TS Magna and running a jumper wire from the extra pin on the TPS to the throttle closed switch will do the same job. The CC GSR/Evo/TR onwards Magna TPS have four pins with an inbuilt throttle closed switch while the VR-4 has a separate switch which also acts like a throttle stop which is vital that it is adjusted properly.

If you get stuck and want a VR-4 throttle body I have one in bits but it's in NZ and I wont be going there until early March.