All the 340/360 a body manifolds interfere a little with the steering shaft in a early a body, but a little grinding and they fit fine. I ran a 72 340 manifold on my 65 Barracuda for 10 years, no problem. It had a 318 with 73 J casting heads. I had to grind a little on the manifold and put a torque strap on the drivers side to keep it twisting over and rubbing the manifold on the steering shaft box collar. I had manual steering. Also, if I remember right the 273 heads are shaped a little different under the exhaust port. When I get home, I will photograph some 273 heads/ early a 273 manifold and with a 340 manifold. And the same with a 360 heads.
Yes, so far I am. I'm on the hunt for 340 manifolds that don't interfere with the steering box. Or if I decide to buy a TIG and weld my own headers. :)