headers on a 400

I'm working with my brother's '72 F100 short bed 2wd. We're dropping a 400 into the truck (don't ask why...it was my brother's deal). Anyway, he ordered a set of flowtech headers that fit the '77-later pickups with the 351M or 400 engine. I'm trying to install them. The collectors hit the crossmember on both sides. I took the crossmember off and now the pass. side hits the radius arm frame bracket and the driver's side hits the steering box. Anyone ever run into this before?

We found the problem. The headers we got were packaged incorrectly...we received the correct part number, but the headers are actually 4x4 headers (for '77-'79 4wd trucks). New (and hopefully correct) headers are on the way.