Would the guys and girls over at DPUG be able to help you out with this? I checked there myself but most everything to do with Autochrome was a thread started by you

I'm not sure exactly what you're after so I'm useless to you, but there was mention of creating colour separation digital negatives... sorry, I want to help because I've seen around how much you want to get this to work, but I'm out of my depth here.
Holmburger's thread about experimenting with RGB colour screens has a comment from htmlguru4242 mentioning that he was working on RGB inks for Epson printers... would that help you at all with what you're wanting to achieve? That particular post is here if it's of assistance: (there was a url link here which no longer exists)
Sorry not to be of any help
Edit: Is this more in line with what you're after? The gentleman who wrote the article is using ICC profiles to restrict the colour gamut to the more muted orange, green and violet palette of old Autochromes. The article is here:
http://therefractedlight.blogspot.com/2011/10/autochrome.html.
At the end of the article is a link to an update with how he created the profile.
Sorry if I'm way off the mark here. I probably shouldn't have responded since I have nothing intelligent to add, but I do so hate to see unanswered requests for help!