I have 3 questions:

1) Where is the casting number located on the heads on a 2.9 and what should they be ? I'm thinking they're under the valve covers.

2) Will a 1989 set of heads fit on a 1986 if they are the same engine but not the same casting number ?

3) What causes a bad shake/vibration when the wheels are turning ? It just started this after leaving a friends house and does it while in neutral and coasting. It is a 1986 2.9 auto w/OD
I checked the u-joints and wheels for play and there is none. The carrier bearing moves side to side about a half inch.

Thanks !