1972/1974 Isolastics and Mounts

I am working on a friend's 850. Upon close inspection, before disassembly, we discovered that it is a 74 engine in a 72 frame. I see that the front forks and swingarm parts are the same between the two years but the isolastics are not. I do not know if it has a 72 or 74 front engine mount/isolastics. Is there an obvious way to determine it? I am assuming it has a 72 mount and isolastics but want to make sure before I replace them. Thanks!

1972
https://andover-norton.co.uk/en/shop-drawing/28/engine-mountings-head-steady-centre-stand
1974
https://andover-norton.co.uk/en/shop-drawing/68/engine-mountings-head-steady-centre-stand#

Or, replace with pre-Mk3 vernier upgrade kits.
https://andover-norton.co.uk/en/shop-details/17047/isolastic-kit-front-vernier-pre-mk3-commando-
https://andover-norton.co.uk/en/shop-details/16920/isolastic-kit-rear-vernier-all-commandos-

This bike has circlips on the isolastics, so it must be a 74...The vernier kit looks like the way to go, regardless.
Thanks for the help L.A.B.