Not necessarily, it doesn't matter what brand of gears, you may need more or less shim.
Get a GOOD service manual, do a Google search on rear end setup for the pattern pictures, and a compressor/impact wrench helps. I've been considering the same thing, plan on spending $100 to 200 for your first one (pinion depth gauge, marking compound, shims, etc.). Is it time to change the seals and bearing while you're at it?
get a factory manual on CD from e-bay. Search for "factory service mustang" or something like that. I got mine for $10 and it is infinitely better than haynes/chiltons.
Just my two cents. I also heard that they would not need to be shimmed. I did the FRPP gears, no shims. Went right in. Just used the shims that were in there already.
just the right tools and alot of patience you definetly need a pinion depth guage and a c-clip tool. summit sells a rear end change kit it will have your shims seals and everything to do it right and they have motorsport gears. dont forget the synthetic lube either. Ive seen dyno results with 5 hp gains from royal purple opposed to a standard 90 weight. It suprised the hell out of me, good luck dude. Oh yeah hope your goin at least 4.10's