I think the 416s are air shocks, no?
Well, I'm not sure. I have 440 HD's on my I/S and I believe 412's on my Std. I do have a pair of Progressive air shocks that I picked up used but haven't put them into service yet and not sure of their # identifier. My 440's seem to be getting weaker. I don't know what happened to the receipt to get them rebuilt and HDL won't / wouldn't answer repeated emails asking for assistance in the matter. (and I spent several thousand dollars at HDL over the years) So to get them rebuilt, it will be on me. Or just get new ones.
My pair of standard duty 440s just got turned up three more turns and are back to good (they did lose some of their stuff, and I'm not sure if it was a small leak or just age). My HD 440s (2yrs older than the standard dutys) are still good on the lowest setting (but I am always solo). HDL sucks (today) , but as far as I know you would always have to go back to Progressive Suspension for any warranty issues (not to
any seller). They will no longer rebuild 440s, but have been replacing them with a newer model (444s?), but you have to have the receipt..... however, if you can't find it, if you used a credit card to purchase them, you
may be able to resurrect that (itemized) monthly billing to satisfy the "new purchase" proof requirement through the card company. True, that will not specifically ID 440 shocks, but a single purchase of around $450 from HDL 8-10 years ago and your word (and the old shocks) might do it.