Replacement panels that take the big back window are now available so the high price for a factory one is now moot. Same for the round bodied 53-56 Fords even though the 56 was the only factory one with the big window. Just get a nice clean complete cab and use whichever window you desire. Most people that bought the big window ones regretted their decision because the sun would roast the back of your neck. JC Whitney, Sears, and Montgomery Wards all had curtain kits to block the sun. No dark tinted glass and a/c in those days.
