Rick,
Changing the calculation to your Biscayne (400 lb lighter than the Bel Air wagon, 3spd) calculates to
2.73
12.06 at 58.3
19.02 at 69.4
12.8 0-60mph
That also seems to me like it would be "seems ok" especially back in the days of less TRAFFIC, and it is about as fast at the "stock 292 powerglide 3.08" in Copo's big wagon. So it confirms again, I think Copo-rat could have an enjoyable cruiser with a 292 or a hot 250 in front of a 4spd automatic.
