and why the 93's were the fastest LT1's

 

Keep in mind that the limited number of '93s with the M28 T56 had a 2.73:1 ring and pinion (GU2) and the M29s got 3.23s (GU5). From 1994-up, the MN6 T56 cars got 3.42s (GU6), so they're not that different, at least stock.

M28 w/2.73:1
1st - 3.36:1 (9.15:1 final drive)
2nd - 2.07:1 (5.65:1)
3rd - 1.35:1 (3.69:1)
4th - 1.00:1 (2.73:1)
5th - 0.80:1 (2.18:1)
6th - 0.62:1 (1.69:1)

Car Test 2000 estimated performance (275 hp LT1)
0-60 ft. - 2.31 sec.
0-60 mph - 5.89 sec.
0-1/4 mi. - 14.55 @ 98.92 mph
Top speed - 156 mph

M29 w/3.23:1
1st - 2.97:1 (9.59:1 final drive)
2nd - 2.07:1 (6.69:1)
3rd - 1.43:1 (4.62:1)
4th - 1.00:1 (3.23:1)
5th - 0.80:1 (2.58:1)
6th - 0.62:1 (2.00:1)

Car Test 2000 estimated performance (275 hp LT1)
0-60 ft. - 2.29 sec.
0-60 mph - 6.50 sec.
0-1/4 mi. - 14.66 @ 96.94 mph
Top speed - 154 mph

MN6 w/3.42:1
1st - 2.66:1 (9.10:1 final drive)
2nd - 1.78:1 (6.09:1)
3rd - 1.30:1 (4.45:1)
4th - 1.00:1 (3.42:1)
5th - 0.74:1 (2.53:1)
6th - 0.50:1 (1.71:1)

Car Test 2000 estimated performance (275 hp LT1)
0-60 ft. - 2.31 sec.
0-60 mph - 5.84 sec.
0-1/4 mi. - 14.60 @ 97.74 mph
Top speed - 150 mph