Ok, here's my first post.
I just bought a "89" 2 dr sidekick that originally had a automatic transmission in it. A previous owner swapped the enging & tranny out with one from a "94" Suzuki that had a 5 speed manual tranny. My question is how is this transmission change going to effect the MPH that's indicated on my speedometer (and the odometer too).
There is a note in the cars file that he gave me that says the automatic tranny has a ratio of 4.625. Also that the manual one has a ratio of 5.125.
Too much for me!

Here is a good site for building your gearing out to see how it is affected:

http://www.solemnwarning.net/transmission/

If you are running stock tires you should be about 10% slow on your speedometer/odometer.  I would use a GPS to verify though.

If it's the indicated speed you're interested in, get a GPS and check it - because at this point all you know is that the engine & transmission has been swapped.  Did the PO swap the front & rear axles (or the ring & pinion gears) also? Did he swap the transfer case (assuming 4WD) or the speedometer drive gear?

Unless you know exactly what was swapped - it'll be probably easier to get a GPS and measure it.

If the axles were changed, then you need the speedo drive gear
from a manual trans T-case, if the axles were not changed then
the speedo is not affected.

The GPS will tell you if there is a change needed, as will a roadside radar
with a speed display

The use of a GPS sounds like the way to go. I borrowed a handheld unit from a friend and will run some tests today and report back. Thanks (should have thought of it myself!)