Thanks all for the replies.
turns out the 90 amp transformer in the machine has no shunts.
I should be able to remove the shunts without damaging the windings as I've had experience with MOTs.
I'm going to either use the output amp adjustment circuit in the old TIG welder or I'm going to build one with the circuit from Dansworkshop. One more question; if I remove the shunts should I push the secondary winding down so it is sitting on the primary like in the picture below:
or should I leave them where they are? (BTW the photo is the transformer in my machine)