big block heads

There are better heads than those out there, IMO I would be looking for 902-346-452-or 906 heads before I would use the 516 heads. The runners are very small in the 516 heads and even porting them they are only as good as the newer heads. They are like 170 cc's and the 906's are 178 cc's and the 346-902-452 are 180 cc's from the factory. It takes alot of porting to get 10 cc's. 180 cc head is what I would use on the 383 and then port the newer heads to get 190 to 195 for the 440 and street use.
You want to use the stock size valves in the 383 heads and use the stock intake valve on the 440 and use a 1.81 on the exhaust side, these are the keys to make them run properly. The 440 needs more exhaust breathing than the 383 due to stroke and bore.