Its the chevrolet Corvair engine!
Actually ahead of its time, its a lot like a type 4 engine, but has two cylinders more
and sports 2,7 ltr in most versions.
Introduced in 1960 (!), it has an aluminium case like the type 4 and about 87,3mm bore x 74,4 mm stroke. The 'inch' sizes are a bit annoying tho
Also unfortunately it runs the other way around, but there were 'reversion' kits made with special camshafts for use in mostly (dune) buggies.
That also gave the idea to use VW cylinder and pistons which gave very huge size motors:
http://www.corvairkid.com/mm01.htm
About 1.2 million Corvairs were made and it has a large following and many clubs and specialised companys exist. Because of the number of cars made, engines and parts are plentifull and cheap!
So: dare to be different and go corvair 6 cylinder!
I already bought me an engine as it does fit very nicely in the engine bay of cars that ran type 4 engine from the factory, like a certain....VW 412S
Greetings,
Walter