94 gt 4.10 gears which speedo gear

You can't. The gear to fix the speedometer doesn't exist. The closest one will still leave your speedometer off by a noticeable amount, and it's a bit fragile. You either need to get a Speedcal to electronically adjust the output from the VSS, or you can have the tranny taken apart and have the driven gear changed. Then you can buy a gear for the VSS to match your 4.10's. Unless you're looking to rebuild your tranny soon, your best bet is the Speedcal.

Oh, and Welcome to StangNet!
 
ok thanks and also my tranny is taking longer to shift after gears wer put in, especially 2nd when i floor it. Does this need to be adjusted too?

The tranny is set to shift at a certain speed based on the gears it thinks it has. Since you have lower gears you're reaching higher RPM's before you reach the speed you used to, so the tranny doesn't shift right. You'll have to change the tranny shift points in the computer, and to do that you'll need a chip for the computer. If you're not ready to go the whole Tweecer route, I recommend a chip & burner from Moates, it lets you change a lot of things in the computer fairly easy.
 
The shift points will occur at slightly lower speeds under low load conditions but it's not a big issue. If the tranny has a 7 tooth drive gear a 23 tooth driven gear will bring the speedo pretty close. The only other relatively inexpensive option is a calibration device such as "speedcal". WOT shift points are rpm determined so speedo readings don't matter.