55 first series has an open driveshaft setup. i am using the stock rear with 3.90 gears. the length of the astro van drive shaft is perfect on mine. the yoke is within about 3/4 of an inch of being all the way in.only change was the crossover u-joint at the rear.this drive shaft also has some kind of balance or vibration wheel on it just beyond the front yoke. it would be great if you can get that disc part number. if i can find a disc that i don't have to chop up to fit ,i would take mine out tomorrow to replace it.
