Thanks for all of the suggestions! After talking to a bunch of people who have done this swap I've decided to change course and center the engine between the frame rails and buy one of those power steering kits that uses one of the later truck steering boxes. I really didn't want to space out the steering box and I tried moving the engine over but it looked really goofy to me.
If the exhaust manifold were the only problem I would have probably kept the stock steering and used a front dump manifold or a (reversed) right side manifold that comes up above the exhaust ports (like this one off a '95 camaro):
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http://img.villagephotos.com/p/2005-5/1008868/95camaro.jpg[/img]
But like I said, even with NO exhaust manifold bolted on the spark plug hits the steering box.
I think the main problem is with the universal tubular engine mounts that all the catalog companies sell - with the "ears" of the tubular mount set in the C-frame rails you can really only move the engine up and down so much. If I were able to position the engine a little more up and a little more forward I think the spark plug would clear and then a forward dump exhaust manifold would have worked, but oh well. Live and learn.
