I wanted to change to 225/60/15 instead of the 235/75/15 like what was on it. I figured that it might be a little lower with out lowering it!! I was told I would have to get the computer reprogrammed for the speedo to be correct.

 

That'll get you about 1.5" lower. Speedo will be off about 5-8mph (it'll read faster than you're really going)

Depending on what year, you'll have to either get the computer reprogrammed, or if it's an early first gen, just change the speedo gear

 

Is it costly to get the computer reprogrammed?

 

Are you using stock wheels?

 

I'm not sure how much it costs to get the computer reprogrammed, but those programmers that plug into the obd port are like $300-$500. They'll do a lot more than tire size, though

 

To work out an approximate change in the speedometer you can use this comparison tool: https://tiresize.com/calculator/

As for reprogramming the speedometer, another option is an UltraGauge (or similar) tool that plugs into your OBD plug. I use my Ultragage to give me a corrected speedometer reading (I have slightly larger tires) but more importantly it reports to me the transmission fluid temperature. UltraGauge OBDII Scan tool & Information Center