I ordered the rearview mirror for the "54 Chev pickup, sold by several vendors. I mounted it above the windshield in the center of the headboard trim piece on my 1942. It looks period correct and works for me. If you were tall, it might sit a little low in the field of vision.

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