36hp ended in early 59; late 59 saw the bastard 40hp. You'd be better off with the 36hp!
I had a '55 westfalia (3rd oldest known to exist - the other 2 are in the Westfalia museum) with a 36hp. 100Kph on the freeway was pushing it, maybe 105 with a tail wind.
A lot of people run 1600's in early VW's; if you ever wanted to go back, it's very easy.
I currently have a '60 DD panel and a '61 double cab - both with 1600's
Check out
http://vintagebus.com some time.