twin engine with 650 ss head for sale

I was at Kempton, UK, jumble today, and there is a Dynamo Dominator engine/plates and gearbox for sale. Vendor says it has a 650 ss head retrofitted. I took a couple of pictures.
It was fitted in a slimline frame and sidecar when he got it, and was running when removed from frame. I have his details if anyone is interested. Message me directly!