Up to 1968 the VW Bus used apretty much normal Beetle transaxle with different ratios for 3rd and 4th, a different nose cone (which holds the incoming shifter shaft) and the ring gear was flopped to the other side of the pinion. These are the "paddle shaft" transaxles.
The 1968 Bus transaxle used many Beetle internals with a larger, sturdier differential with a deeper r&p and side bearing screw adjusters. These used splined output shafts with a flange to attach a cv joint. The 1969-up Beetles (and 1968 models with an autostick transaxle) used essentially the same "paddle shaft" transaxle but with a differential that had a male splined trunion shaft onto which a cv flange was retained with a snap ring.
The Snowtrac differential in your photos has a female splined side gear (to receive the spline shafts of the Variator) which is a bit different. Other than that it looks just like an aftermarket "Super-Diff" which incorporates 4 spider gears instead of the normal 2 of a stock VW.
I would say you could use a Super-Diff with the Snowtrac side gears and nearly any VW IRS transaxle and be good to go.