[Bill Hanlon]

I don't have one, but to help in your search the 1960 Pontiac Chassis Parts manual has part # 5670049 for the 56 & 57 HydraMatic yoke and 5673335 for 58-60. Funny thing is, the 1966 edition of the same manual has 5678648 for the 1958-60 (and some later) HydraMatic front yokes. Neither manual goes into the differences between the yokes. However, the rear planet carrier assembly (which provides the splined output shaft) is a different part number from 56-57 to 58

But the good news is that same manual calls out only one part number for U-joints from 1956-59 no matter what transmission. So as far as connecting the tranny to the driveshaft, you should be able to use the yoke from the 58 transmission to connect to the 57 U-joint.