school me on a 5.9 magnum motor.

I built a 5.9 with Edelbrock heads, and a 340 with X heads about the same time.
I broke both of them in on my engine start stand, using the same headers (generic steering thru the headers car style).
Using the same name brand header gaskets, with no leaks.

I then had a change of plans and put the mag in my 78 W150, and bought the standard truck style headers (Headman). Never did have gasket issue.

My guess is the exhaust ports are the same, but again, not 100% sure the Edelbrock used a factory magnum port.