I've seen both #62 and #48 heads on 428 A/T GP's. I think maybe the #16 heads were used on M/T cars but can't say with certainty. Maybe the #48's were used on the XG 428HO's. To the best of my knowledge they are all the same head: valves, springs, screw in studs. Just a different code number to ID application.
My guess is that the std rear end was a 3:08. That is what came on my Bonneville with std 428 and A/C.
Several years ago I parted a Bonneville Brougham convertible 428HO. Std rear end for B body cars with 428HO and A/T was 3:42. 3.23 with M/T (very few made, maybe less than a dozen). Posi was not std. You had to order that.
BTW: They only made about 726 YK coded 428HO's for the B body cars and about 1,240 XG coded 428HO's for the GP's. Or phrased another way only about 2,000 units for a total production run of some 450,000 cars: 250K Catalina's; 100K Bonneville's; 112K GP's
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'69 Bonneville convertible
Warwick blue/ parchment interior
53 option accessories
2 more to go :-)
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