In my '54 630, which has a large steering wheel, I raised the whole seat track assembly, 1.5" which helps. If you need more room, I put an S-10 seat in my 1st. '47, they have thin backs.

Ed

Last edited by cletis; 02/03/2016 1:29 AM. Reason: overrode auto censor
'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires.
'47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle.
'54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed.
'55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.