Rearend question

[biscuit]

I,m working on a 54 1/2 ton short that's getting heidts mustang 2 front and chassis eng. rear . I'm going for as low a drop as i can without bottoming out on flattened squirrels ( NO BAGS just a static drop ).The question is i have a 70 nova rearend with 2.56 non possi center which is a nice match flange to flange with the stocker but was wondering if a slightly narrower diff would help with rear fender clearance I have no problem with tubbing the box for clearance.
Just would like some thoughts before i spend some money on a set of 3.08's and a possi
Drive train is 275 hp 350 and a 700r4 with 28" tires
Thanks

[_Ogre]

http://www.chevytrucks.org/tech/ifs&rearend.htm scroll way down, lot's of good rearend info
i'd sort of like to see what mpg you'd get out of that 2.56 rear gear set
cruising speed would easily be 90 mph or better

if your the same width as stock, wider wheels and tires can be accommodated with wheel offset
a little narrower rearend will make it easier to remove the rear wheels

i have 350 hp w/efi, 700r4, 28'' tires and 3.27 gearing, my truk gets 20 mpg cruising at 75 mph