Well done Paul on the Rings Paul, they've helped me a few times.
Not sure on the bearings?
Gasket size Im unsure of. Basic rule for crankcase to barrel is, fit the barrel and measure the distance between barrel end surface and piston to find your thickness,and use the appropriate material allowing a few thou for crush. Crankcase halves are usually dry,sealant or of the thinnest material...eg paper thickness.
As for the head, see if there is any salvageable material to measure,or just run std Victa 125 thickness?
Anyways glad you got your rings, cant wait to see it running:)
