Not my idea (and not a 3.2), but my engine:
I agree that the new mat sit just fine in there without any glue but in case vibration and heat change that I fashioned 2 strips of aluminum to go from clip to the cross member as a bent press fit.
No claim as to performance, my car came to me with a mat falling onto the motor which I promptly vacuumed off and ran like that till mid-last year when I took the motor out to rebuild it.