Hi my steering cars wheel wont turn...without encountering a nasty resistance like its catching on something.....power assistance seems gone....small puddle oil under car....any ideas what this could be and.....

I are the racks for the 3.6 interchangeable with the rack for a 91 4.0 litre?

 

It sounds like your power steering system is empty.
Check your power steering reservoir.
If empty refill, start the car and turn the steering wheel from lock-to-lock ie hard left and then hard right to bleed the system.
It sounds like you have a leaky system most likely in the steering rack.

 

You need rebuild the steering rack

 

Looks like the lower steering column bush is impacting on the exhaust pipe...shouldnt do that