I think they brought out the 40 hp engine in 1965. Before that, it was 36 hp.
I would guess that 75 hp would be adequate for a 2000 lb. car of that era.
Used to drive a 1965 Austin 1100..49 hp...manual. Lots of pep and a hoot to drive.
Mine was indeed a 40 hp engine. The 1972 Super Beetle has a 72 hp engine. It didn’t weigh 2000 pounds.