Welcome to the site.
If you check out the NFA/Class III section you might find a couple threads about suppressors that could help you out.
for .22 supressors I would go with either an SWR spectre or a Silencerco Sparrow
for .223 I would go with an AAC M4 2000 or the M4 1000 if you're on a budget
I'm not sure about the .308 can. I've never had the desire to have one so I've never looked into it myself.
I talked to the guy at CHA about this he had some YMH can's
600 for steel
900 for titanium
And 75.00 for the threaded end piece for each gun it will go on your 308, and come right off and go on your 223, or 22