diff help

[Fozz]

before yous all start yes i have searched just want a little info on diffs

1. im looking for an f or g series diff which car is the best one to get it out of (i want the width of the diff to be close to the standard width as possible)
2.did either diffs come with a 3.9 ratio

also i heard that the g series is overkill im running an sr20det is this true or will it be ok

cheers

EDIT forgot to ask do u need a custom tailshaft for the f series or can u use thetarago rear half