My parts jeep is canadian so km per hr and my current jeep is American (mph) but the gauges are bad so I was wondering what would happen if I swapped out the mph dash for the kmph

 

You'd suddenly have the urge to drink Canadian beer, cheer for the Maple Leafs, and say "Ay" all the time.

Nothing would happen. The PCM doesn't have a clue where it's at - USA/Canada, nor does the instrument cluster. You'll just have to explain to the cop that stops you for driving too slow or too fast....

 

That's what I'm asking will the speedo read properly? Since I'm swapping in gauges set for km instead of miles

 

It should all work except the mask is metric. I think that I remember seeing someone making new masks so you could replace the mask to display US values.