YES 5.9 Magnum manifolds work in early A bodies. Here is exactly how!

The JGC driver's manifold will not work on an A body if that's what you have. The JGC had the starter on the passenger's side which made a lot of space on the driver's side. I tried to install the 2 1/4 inch JGC manifold on my '69 Barracuda. There's no way it will fit unless you're able to drive your A body without the starter!! OR....install the JGC motor in your A body so that you have the starter on the passenger's side!!
No mine are not JGC they are standard small magnums off a 01 ram I believe