They have a recessed oil filter boss (but then all the early Chevy II V8s do). Other than casting numbers I wasn't aware that there was anything that would differentiate it from other early Chevy II blocks.
I used to have a 64 Chevy II 283 sitting on a stand next to a 65 Chevy II 283 and I couldn't see any difference. They were identical as far as I could tell. If there was anything different it couldn't have been too special.
I've been told the 65 was the only one with the recessed filter housing. Did not make much sence since all early Nova's were same configuration. I was being vague to see how consistant the replies were. What would some of you estimate value at? I've got one sitting, not sure what I want to do with it. I really couldn't care less about much stock stuff.