1961 Seat Width

[The1960APE]

I just ordered my seat for the 1961 Apache, The company I ordered it from offered two widths, 50" & 58" the seat is a 40/20/40 split. They kept telling me that everyone with that year truck runs a 50" wide, When I measure my cab from door to door I am at 62" or 64" I told them that 50" would be to narrow, they were a bit argumentative about it but I insisted that they build a 58" wide.
That being said I went out to my buddies 88 single cab, from inside door panel to door panel it measures 60" and has a 57" seat.
Anyone care to chime in about which width I need? Am I missing something?