[Safari Larry]

Good news, I used a long round file to knock out some of the rust buildup from inner 56 head and the 57 tube now inserts freely into the head! Assuming the 55 head is the same as 56, the 58 tubes will work.

The tube will insert into the head from either direction which surprised me. So that leaves the question "which way should it be inserted?" Remember for 1957-59 there is a left and a right tube. It fits better in one direction (flatter side towards exhaust) than the other so that's the way I would install it. It looks like it would work about the same installed from either direction so it may not matter.

I cleaned up my 56 tube and it is brass. That agrees with head casting date, J225 = Oct 22, 1955. Photos attached of the 56 brass tube and 57 stainless tube.