As to your original question as to whether you can use your 216 manifolds on the 235 - the answer is YES. I have a 54 235 in my 39 PU and am using the original 216 manifolds and carb and exhaust.
However,if you haven't installed the 235 yet I would opt to go with the 235 manifolds, carb and exhaust. (Note: if you change the manifolds you have to change the carb too.)
