What should I do?

If you like the look of headers sticking through the inner fenders, and down inside the wheel wells, use the headers. But you might find you need to wrap them to keep other stuff cool in the engine compartment.

Personally I don't like that look, it's just not quite right. I plan to use the 340 HP manifolds on my '65 Barracuda with my 340. I have manual steering. This guy here has done it - http://www.ultrajosh.com/myshop.htm

Seems to me he had power steering but had to change the shaft and used a Flaming River u-joint.

If you decide on the headers, I might be interested in buying your manifolds. I'm missing one.

Thanks.
Neil.