maybe you're just some bigger than folks were back then
55.5" outside to outside of the arms that the back mounts on - notice that those 'hinge' arms rest on adjustable bolts that are in brackets that stick out each side - the adjusters set the vertical angle of the back, and the brackets those bolts are in are frequently twisted/bent down/broken by years of abuse .... my seat all the way back on the tracks leaves a couple/few inches to the back wall without hitting anything .... the LCF shouldn't really be different there, see if you can adjust the back angle
Bill
