My 68 valiant has a km speed odometer and without taking the gauges out it looks like its a decal laid over a mph original. I was just wanting to know it this was a common practice for cars that were sent to canada and if so will it come off clean with a heat gun?

There were KM decal overlays such as you describe offered as aftermarket "conversions" in Australia when that country switched to the Metric system of measurement in the mid '70s. I haven't seen evidence of similar such conversions being offered in Canada after 1976, so if that's what you've got, it'll be the first. Please show us some pictures!

I don't think you'll have difficulty removing the decal. You likely won't need a heat gun, nor would you want one -- that's much too hot and you'll likely damage the speedometer. Warm it up with a hair dryer, then peel it off, then go over the speedo face with denatured alcohol to clean up the adhesive residue.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

That is definitely an aftermarket "conversion" decal, very much like the Australian ones (except the Australian ones didn't have smaller MPH numbers, because there was no bordering country that still used miles as is the case in Canada). Interesting! Y'might leave it on as a conversation piece, since you can still read your MPH.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Little hard to read at night but all my friends are telling me the same to leave it. Funny story my chebby loving father in law was checking out the valiant and said HOLY $#!+ its got a 160 mph speedo! I started rolling laughing

I'd have to leave that on there

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1972 Plymouth Duster 225

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一期一会
Too many people who were born on third base actually believe they've hit a triple.