As a child, I used to love looking at my dad's old Kodak slides on the carousel viewer. In a darkened room, something about the hues and shades of the 1960s on Ektachrome film projected on the wall just seems better than real life. On ebay right now, a seller named Motorbookbroker has some absolutely fantastic medium format color transparencies for sale depicting racing in the mid 1960s. Most are from Can Am and sports car races, and since they are original slides, if you buy them, you buy the rights to them as well. I'd say that's pretty swell.
I have selected my favorite 8 of them in a gallery HERE for your viewing pleasure. I have no affiliation with the seller and I hope he appreciates the free advertising!