Regarding the MK3 type head steady spring- I became a big believer in the benefits of this after removing the front iso recently.
Several years ago I played with the spring tension and found that too little tension resulted in increased vibration as did too much tension. Increased vibration might be the wrong term as the spring changes brought vibration into the previously smooth as glass zone from 3000 rpm to redline.
After some experimentation the right setting was found and the wide smooth zone returned.
It turns out that the smooth zone is only truly smooth when all the weight of the engine is held up by the spring.
The front iso bolt can be slid in and out easily as the engine is perfectly suspended by the spring.
This also prevents sagging ISOs.
I'm quite sure these ISOs are original but they are not at all sagged, the bike runs smooth so I left them in.
Your head steady, if stock, will be the strong boxed in type, but won't have a spring so you might consider adding the MK3 spring to it.
It's also quite likely that your ISOs are sagged as that seems to occur fairly quickly without a spring type head steady. So my thoughts are change to new MK3 vernier adjustable ISOs (if your ISOs appear bagged and sagged) plus add the MK3 heady steady spring arrangement. On the off chance that your existing ISOs look good, you could just shim them by the book procedure and try just adding the spring. That won't cost much and it might be interesting to see what occurs with the single change.
Set the spring up so that there is zero weight on the iso bolts.
My MK3, once above 3000, is as smooth as any modern I've ridden.
Glen