LT1/LS1 6 speed/gears????

I have a 96 WS6 6 speed TA,
My friend has a 99 Z28 6 speed......

His car is about 400 rpm less in 6th gear on the highway???
WHY???

I thought 94+ have .50 6th gear ratio's???
I thought all T-56's come with 3.42 gears???

Im reallly curious about this and we cant figure out why........
(he thinks he has 2.73 gears)

Do you both still have the stock tire size height?? ALL Z28 6-speeds have 3.42 rear ends stock. The Tacs may be off a little. I hear they are not very accurate. I am 1400 @ 60 in the '02 and shows 1500 @ 60 in the '95. Later>>>>>