Root is correct. The Jeep rock crawlers use the SM420, especially for the low first gear. There is a company called Novak that supports the SM420 for the purpose of that crowd. They sell all the parts you would need if you can't find them through the normal Chevy truck channels.
Kent


1937 Chevy 1/2 ton
1942 Chevy 1/2 ton
1947 Diamond T Model 509
1951 Chevy 1/2 ton
1950 Chevy COE Model 5700 ~ "Barney" ~ And more pix