The 250 will be a little hard-pressed to maintain highway speed, particularly on an upgrade with a gear that tall. Also, the non-synchronized 1st. gear will be all but useless in traffic, requiring a full stop to get it into gear without grinding, and a very quick over-rev if a 1-2 shift isn't made within a few feet of getting moving. Using 2nd. as a starting gear might require slipping the clutch a little. Even a 3.08 gear would be more likely to be user-friendly. The 2.73 was a popular option with big block engines like Olds, Cadillac, and Buick, with lots of low-end torque and an automatic transmission. Those engines could be run just above idle at highway speeds for better gas mileage. Not good with a stick shift and a low-torque engine!
Jerry