What kind of rear end do I have?

[Stang_ROTY]

To make a long story short, I bought a 93GT minus the motor and tranny that is an ex-drag car. The guy wa doing 9's in it so the rear end is beefed up. From what the previous owner told me, it has 3.73's in it. From looking at it with the slicks off (the slicks have metal valve stems) I can tell it's probably not the stock rear end, but it is an 8.8. It has extra long NHRA certified type lug bolts, a aluminum rear diff. cover, and what seems to be substantially larger axles. It seems much more stiff than my stock 87 GT rear end 'cause I jacked it up with the slicks on it and the passenger side rear will rotate slightly then lock and my 87GT just rotated freely. Anyone have any idea as to what type of rear it might be? Also, I should change the fluid in it...what type of fluid do I use and how hard is it to change it??

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Almost done!
93 GT, Dynamic C4, 8 pt cage, chute,
Sothside Machine bars & Sub-frames, 3.73's
'69 393 stroker w/SRP pistons, Edlebrock Performer heads, Performer RPM Upper & Lower Manifold..Crane Gold 1.6 Rollers Comp Cam..BBK 70MM TB, ceraminc shorties & H-pipe w/cats..30lb Injectors..Cartech Fuel System