The Speedibrews Celer-41 kit sounds like exactly what you need. Not used it for a long time as I have my own brews for that, but it does give timings for room temp C-41, I doubt it will give super-accurate results for 'critical applications' but for cross-process et al, it should be great. Silverprint should stock it, or they can ask Mike to make some kits for you.

Speaking as someone who knows about this sort of thing, steer clear of shooting C-41 material over about 8-10 years old, nothing over 1999 expiry unless you know it has definitely been cold-stored. That is unless you're after magenta/green effects, in which case go for it. Old Fuji has a tendency to fog however, which might be tricky to print.

PM or email me if you need specifics on any of it.

Have fun!