Z31.com Wiki

Harmonic Balancer Information

Because of the different years and engines, there were four different harmonic balancers used on the Z31's VG30 engines. Below is a chart to help determine which one you want to use.

Year	Engine	Aspiration	Part Number	PS Pulley	AC Pulley	H2O/Alt Pulley
1984-1986	A/B Series	non-turbo	12303-V5020	V-Belt	V-Belt	V-Belt
1984-1986	A/B Series	turbo	12303-V5320	V-Belt	V-Belt	micro-V
1987	A/B Series	all	12303-F6100	micro-V	micro-V	micro-V
1987-1989	W Series	all	12303-21V10	micro-V	micro-V	micro-V

You can use the A/B series balancers on the W series crankshafts if you get the spacer from Nissan (p/n 12308-V5321).

You should be able to use a W series balancer on an A/B series crankshaft if you get a slightly longer bolt with matching threads.