There are several VW industrials as follows: The 1192 CC is the "40 HP" or "1200". This engine has a prefix something like 106 instead of a letter preceding the serial number. The 40 Horse Industrial only produced about 35 actual horsepower. It had a predisessor that I don't know much about except that is was a 36 HP, had a cast in place generator pedistal and the Camshaft rode directly in the case with no bearing inserts. This made it a poor candidate for rebuilding. It only came in 1958,59 and some 1960 machines at which time they up graded to the 40 HP. The 40 HP has real Cam bearings but still wasn't a very good choice for rebuilding.
VW Car/Bus/Transporter/Karman Ghia engines all have an entirely different serial number series and can all be identified by John Muir's "Idiot Book". They usually have a letter designator preceeding the serial number. "F" was the 1300, only produced in 1966, H is a 1500, AE & D Motors are 1600's. Briefly, probably for one year, ST4's came with 1500 CC 50 HP Motors.
All the Snow Trac's after this (around 1967) came with the "1600", 126 Motor. This is a very good engine. It had very high compression, 10 to 1, and was 1584 CC. These engines produced about 53 HP. 126 Motors have 126 preceeding the serial number on the Block(Below generator pedistal) and on the Fan Housing. But Beware, the Fan housing could well have come from another engine. You have to go by the number on the Block. 126 engines also had 126 on the intake manifold and it was larger diameter than what came on the same year bug engine providing less restriction and better flow, consequently More Horse Power.
Most all of the VW industrials had a unique spring loaded distributor rotor that prevented the engine from being over-reved. It was designed to ground out over a certain RPM. Some special order Snow Trac's came with Porsche Industrials. These are distinctively different. Pictures and identification can be found elsewhere on this forum. 2 Carbs, Rectangular exhaust ports, Slanted or angled generator mount, 5 Main Bearings, External Oil Filter and the serial number is preceeded by a Star and the letter 'P'. They were also 1600 CC's and produced 65 to 75 HP.