ok guys thanx heaps for the info tried searching but fail you guys are the shit ta, the diff is getting delivered 2moro if its an e-series or f im not fussed either way because the t18 lasted me a long time and im only making 240hp so if its an e-series its only .4" smaller 1mm smaller in axle width aswell to the f-series so the e-series will still be a good upgrade and cheap also

t18 6.7"
e-series 7.1"
f-series 7.5"

YR20 Solid Axle (leaf) E292: 7.1", 4.10:1, 2 pinions, Open
4x114.3 1415mm Drum
YR21 Solid Axle (leaf) E282: 7.1", 4.30:1, 2 pinions, Open
4x114.3 1415mm Drum
YR22 Solid Axle (leaf) F282: 7.5", 4.30:1, 2 pinions, Open
4x114.3 1445mm Drum