Th 335 horsepower rating is a bit on the lean side, this was done to keep insurance companies in the 60's from charging high insurace premiums for high powered vehicles. Estimates were that in a un-modified state, a stock CJ was closer to the 400 horsepower mark. Check out this web site for more info on Cobra Jet engines and cars:
http://www.428cobrajet.com
Hope this helps, Bart.