http://www.stovebolt.com/techtips/gauges/speedometer/index.html

http://www.stovebolt.com/techtips/interior/gauge%20cluster/index.html

The above tips are not for your year truck, but maybe you can pick up some helpful info.

As stated above be sure the surfaces are clean.
I gave each surface a small spray of glass cleaner before applying the decal so I could reposition it, if needed.

Take the advise given on the odometer/spedo also. Otherwise the numbers will not index properly.

Good Luck