[JAM1775]

TKO 600 will give you a long first gear without the higher revs. With 331's you could make 45-50mph easily in 1st without screaming revs. Perfect for your BB.
I also think the best OD for your BB is the Tremec 600's .064. You have huge BB low rpm torque.....so cruising at 60mph at 2000 rpm would also be perfect . My motor makes big torque and cruises at 1850 / 50mph or 2100/65 mph..no problem with the Tremec 600. Making your 427 rev and stay at 2800-3200rpm along the highway when it could effortlessly be pulling along at 2000-2300rpm make little sense to me.