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Old October 4th, 2020, 06:35 PM
BillT BillT is offline
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Join Date: Jan 2013
Location: Moneta, VA
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Default Re: Transmission identification

If it's an SM 420 for sure, the Date Code reads April, 22, 1958 (possibly 1948 if they made them that early, or 1968 if they made them that late).

Also curious. If it got changed from a 3-Speed to a Truck 4-Speed, did they change the Floor Hump or does it still have a Low Hump?
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Drove and owned many, but some of the more interesting ones were:

-'60 GMC 2500 Dump, 305 V-6
-'62 GMC 4000 Flatbed, 305 V-6
-'62 GMC 6500 Flatbed Dump, 478 V-6
-'67 GMC 7500 Box, 6V-53 Detroit
-'71 GMC 9500 Flatbed Dump, 637 V-8
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