I just addressed this issue on my '55.1.
The original truck fuel pump on the '55 235 has the metal cap (no glass globe) and the fuel line runs parallel to the engine block. GM subsequently modified this pump to accomdate the engine mounts on the later cars, requiring that the fuel line be off-set by 20 degrees (the input line angled away from the block and the input line angled towards the block). The engine mount in the '57 car required this.
On my truck, the PO had replaced the original pump with the later pump with the off-set. So either one would work, but I chose to go back to the original setup and adjusted the fuel lines without much trouble.
If you want the pump with the off-set, they are widely available and fit all of the 235's. Classic Parts has it and so does Napa. If you want the pump without the offset, Jim Carter has them. Note that the various listings do not clearly distinguish this, and in later years GM sold the pump with the off-set for all applications, including the earlier trucks that did not need them.
I used Jim Carter's pump. Went in easy and works great on my 55.1!
If you don't care which pump your truck originally came with, just match the one that's in there (likely the one with the off-set) and avoid fiddling with adjusting the fuel lines.
