Bessie, if you are curious about your rear axle ratio, try this: (Yes, I know I have posted this a thousand times, but it bears repeating)
"Jack up one tire if you have an open diff, or both tires
if you have a working posi or locking differential. Rotate the
tire one full revolution for posis and lockers and 2 full
revolutions for open diffs. Carefully count the number of full
revolutions the driveshaft makes. This is your gear ratio. In
other words, if the drive shaft turns 3 & 3/4 turns, you
probably have a 3.73 gear ratio. Turning the tire for twice the
number of full revolutions and dividing the drive shaft
revolutions by two will give you a more accurate
reading." (quoted from West Coast Differentials)
If the rear end is from an automatic car, it's probably 2.73 or 3.08 (if it's a 10 bolt rear, 12 bolt would be 3.07). Pretty tall when combined with a 3 speed manual.
Otherwise, use the Turbo 350. It has an overall first gear ratio (when combined with the torque converter's "slip"reduction) of 17 to 1, which will work OK with your Impala axle.
283's don't work well with automatics; the 3" stroke is better suited to a manual trans combined with a "deeper" axle ratio like 3.73, or even better 4.11
