TomR, the 216 car for my yr is listed as 85hp, the truck 216 for the same yr is 78hp. I don't know how GM changed stuff to alter the HP.
Various items are different as already mentioned, fibre or alloy timing gears etc.
Whitedog, the 235 is an increase in bore (3 1/2 to 3 9/16)and stroke (3 3/4 to 3 15/16)