Why stop at Kodachrome 35mm film? If you can afford to bring it back and use it, do so in 8x10 sheets!
Kodachrome 25, of course, please. None of that tepid 64 speed product. Slower film is a more legitimate challenge when you're hanging onto a cliff with two fingers, trying to shoot an SLR in the other hand, and then a wasp lands on your nose! (That literally happened to me way back when).
As for slide shows, the pros typically underexposed Kodachrome a little. A close friend of my brother in the 60's made his living winning international slide shows. But for reproduction or duplicate purposes, an underexposed chrome was, and still is, a headache; likewise an overexposed chrome.
A few people started shooting Fujichrome 50 a half stop slower when it came out, combined with modest pull processing, for sake of less contrasty Cibachrome printing. But the daylight Ektachrome of that era was still Ekta 64. Regardless, unsharp masking worked a lot better for taming print contrast. Once Velvia showed up, masking had to become downright brutal.
I've never head of anyone overexposing color neg two stops, unless it was my Mom with her Brownie and Kodak Gold, who didn't even own a light meter. That's insane. And with today's CN choices, you want to stick to box speed for best results, especially with Ektar.
