The fork looks like a Ceriani Roadrace fork, also known as the GP fork.. the new ones are a bit different. The blown v-8 I think had the double mount fork, that is one can be for brakes and the other for brace if needed. The Cerianis I got both are made for handlebars not clipons. but they made a top tree that was smooth fore clip-ons as far as I know. Sometimes trees can be found seperate, they are marked ARCES, I think it is the forging company that struck them. If you get lucxky you may score a whole front end listed as such. They were used on XR 750 and a few other bikes.
One note about them the lower leg or slider is amazingly thin, in the narrowed section, it will scare you if you measure it.. but keep in mind they carried many a double engined bike down the track, pretty sure a few of them lofted the front end, and came down less than gently..