ring is typo tire rim
VS is the old Vintage Speedster out of Hawaiian Gardens. Vintage Motor Cars is there now. Like I said going from IRS to SA gives more room in rear for wider wheels and tires. My CMC is classic body on '71 IRS pan and with Porsche 2L Fuchs (5.5x15") with 185/65x15 tires I have about a 1/4 clearance with rear fenders. So agree SA is handling step backwards but reducing rear track is costly. No way I could add disc brakes to rear of mine without costly narrowing of rear control arms and shorter axle shafts. Yes welding is require to change from one to another. Note - the VW pan has to be shorten ~11" and welding is required there too.
Does a VW pan come from MX with the body? If so can it be registered in US easily? Bodies and subframe will fit on either IRS or SA VW pan.
Have you looked at used/unbuilt FF/CMC Speedsters in US? All the bits and pieces you will need to complete your can be quite costly - plus build manuals are readily available.