Big block intake swap questions

If the manifold you have is really off a 413, you can stop right there

B / RB engines are what is called "B" block and "RB" for "raised" block

This includes a fairly rare early 383, not often seen

and 413-426-440

All the low blocks are (I guess) the rare old 350, and 361--most 383s and all 400s

The raised blocks used the same heads, pan and timing cover. But the raised block causes the heads to be slightly "wider apart" so the valley cover and intake won't fit between the two series

Other difference are the cranks, pushrods and distributors. along of course with pistons