I just went back and looked at the pic Jim Pomroy took of his steering shaft location. Those long tubes will clear that easily. No problem.
The header tubes as they exits the port come out level with the ground, they done slope down much if anything. They pass under the upper frame tube with about 1 1/2" of clearance. After they exit the frame, then they sweep down to the collector.
Hopefully I get you some pics later tonight. In the mean time I looked at a WC car at Wire Wheel. The pics of the engine showed the way the hearder run fairly clearly. Worht a quick peek.