Brilliant thanks Eddie yet again xx I will do that and report backSome MIGs have the two laminated cores - the main transformer and the choke - welded together, one on top of the other. However, they work as separate components, the windings and the magnetic fields in the cores are self-contained. Perhaps the "stacking" is just to save mounting brackets and bolts. If yours are like this, and you cut the welds, then the old 170 Amp choke can certainly be used with the new transformer.