I believe you can use the "pumpkin" out of up to a 1962 but someone needs to verify that. However, I do know you can use a 55/56 as I put one in my 52Panel. 485window, I'm not sure abut the 48 but "almost sure". You just pull your axles out, then unbolt the torque tube rear end and pull it out. Then just stick the "pumpkin" back in your housing and use your same axles. I'd probably put a new pinion seal in the "pumpkin" before putting it in and also replace the axle seals...as well as check the axle bearings.
Hope this helps.
