Gears and speedometer for '02 GT

[BryantD]

I posted a couple of times concerning exhaust and other possible bolt-ons. Based on the responses I've gotten (plus reading a bunch of this forum) I'm going to do the Gears first (going with 3.73's; just in case I ever decide to add a blower!). I can get the Ford gears locally for $199.00 (vs internet for $179 plus shipping; I figure it's a wash so I'll buy locally) and $250 to install them. Is this a resonable price? A fellow at Austin Performance said I need a $11.95 plastic gear to adjust my speedometer; is this correct? I read Hammer's FAQ and he indicated you need a $100 to $140 Speedcal so I'm confused; which is it? Thanks for your help!