The SM 420 was used from 48 to 67. The SM465 was used from 68 to about early 90,s. with various changes. The only way you can decrease the engine rpm at highway speeds is an o-drive trans. or higher gear rear end.
They say money can't buy happiness. It can buy old Chevy trucks though. Same thing. 1972 Chevy c10 Cheyenne Super In the Gallery Forum
