My Diamond T, built in 1947, has a Hercules JXC engine with aluminum pistons. This engine is a pre-war design, flat head (L-head) six cylinder. They knew the advantages of aluminum back then and pointed this out in their advertisements.

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