15W-40 is the recommended weight, and it MUST be API CJ4 rated oil - gas engine oil will not suffice, nor will the API CI4 oil used for pre-2007 engines.
about 67 hp
67 + 67 + 67 + 67 + 67 = 335
One key difference was the engine. The 66 VW Bug has a 50 horsepower engine and the 67 had a 53 horsepower engine. The late 67 VW Bug suspension had an integral sway bar in the rear.
1 and 67
You use *67 before the number
F0 1966/67 1300cc
HO 1966/67 1500cc
F0 1966/67 1300cc
Volkswagen designed all its "Upright" engines, which your Bus has, to have the same external dimensions. A 1600cc engine will fit fine, and it's what I would use. You will need to use the flywheel off your old engine because the 1600's flywheel is 20mm larger.
If you are asking if a small block chevy V8 flywheel (most common engine in a 1967 Camaro) will work on a Pontiac V8 (most common engine in a lemans), the answer is no.
*67
Just over 67 cubic inches