[GTX JOHN]

I believe they made a 413 engine well into the 1970s. It was in motor homes,
stationary engines, Oil well equipment and some HD trucks.
Very little interchanges with the car engines except block.
It has much higher cylinder heads with a wider intake by about an inch or more.
The exhaust manifolds look similar to a 340 but larger. Bigger water pump and different location for it. Several other distinctions are easily observable.
It does have a windage tray that you can use on regular B engines. I have scrapped all mine years ago.