Kamaran

Have 3 options for gears! I'll be getting them on saturday! I have 31's with a 5 speed and won't be going bigger! 307 gears right now. Getting complete axles since I have a D35 & D30 disco and I want to ditch both!
Anyway options are
HP d30/C8.25 (3.55)
HP d30/C8.25 (3.73)
HP d30/D44 (4.10) its also got a command track...both wheels spin the same direction, so its got to be a LSD or Locker right?
Axle doesn't matter to me but the D44 has a "command track" and would a LSD or locker out back..a C8.25 is pretty damn equal to the D44 so no sweat there! Now I did some research on speed & rpms...Heres how it plays out! I'll post max speed per gear, and MY common cruising speeds and the rpms at those speeds! Highlighted RPMs are the gears I'll most likely use at the mph stated!

Ax-15/31's/3.07's
1st- 43mph
2nd- 71mph
3rd- 115mph
4th- 165mph
5th- 209mph
Cruising
35mphs in 3rd & 4th gear: 3rd-1700rpms. 4th-1200rpms
50mphs in 4th & 5th gear: 4th-1700rpms. 5th-1300rpm
70mphs in 4th & 5th gear: 4th-2400rpms. 5th-1900rpms


Ax-15/31's/3.55's
1st- 37mph
2nd- 69mph
3rd- 99mph
4th- 143mph
5th- 181mph
Cruising
35mphs in 3rd & 4th gear: 3rd-2000rpms. 4th-1400rpms
50mphs in 4th & 5th gear: 4th-2000rpms. 5th-1550rpms
70mphs in 4th & 5th gear: 4th-2700rpms. 5th-2200rpms


Ax-15/31's/3.73's
1st- 36mph
2nd- 58mph
3rd- 94mph
4th- 136mph
5th- 172mph
Cruising
35mphs in 3rd & 4th gear: 3rd-2050rpms. 4th-1450rpms
50mphs in 4th & 5th gear: 4th-2050rpms. 5th-1650rpms
70mphs in 4th & 5th gear: 4th-2900rpms. 5th-2250rpms


Ax-15/31's/4.10's
1st- 32mph
2nd- 53mph
3rd- 86mph
4th- 124mph
5th- 156mph
Cruising
35mphs in 3rd & 4th gear: 3rd-2250rpms. 4th-1550rpms
50mphs in 4th & 5th gear: 4th-2250rpms. 5th-1750rpms
70mphs in 4th & 5th gear: 4th-2900rpms. 5th-2350rpms

Which should I go for guys? The 4.10s is what I want...but whats the best cruising rpm on the freeway? I was told keep it 2000rpms or lower..but I travel at 70-75mphs and don't know it 2300-2500rpms is gonna be a mpg killer? Obviously 4.10s is the perferable choice and should help me in town with the get up and go..so plus there but what about highway cruising?