Is this the kit, and all I would need to convert my 89s rear end to 5 lug?
http://www.fordracingparts.com/parts/part_details.asp?PartKeyField=1675-LUG REAR BRAKE DRUM/AXLE SHAFT KITS 1979-93 MUSTANG/CAPRI
M-1126-A*
Suggested Retail $468.00
Package Dimensions: 12.00H x 11.25W x 36.25D
Weight: 57.00#
Catalog Page: 148
Instruction Sheet: Click here to view the parts instruction sheet.
Warranty Available: No
M-1126-A* 28T Differential
This kit includes 1 pair of 9" x 1-3/4" brake drums with (5) mounting holes on a 4.5" diameter circle and 1 pair of 28T axle shafts with mating 5-lug bolt pattern. Permits owners of 1979-93 Mustang/Capri vehicles with 9" rear brakes and 8.8" rear axle with 28T differential to fit 5-hole, 4.5" diameter bolt circle wheels to them.
Local dude has one on craigslist for $95, still in the box.

I have 4 94-98 tristars with decent tires. If I can spend $95 plus some diff fluid and do tons of burnouts, I'm all over this!