Redi-Strip is the chemical de-rusting place, tho I doubt you'll find one in enviro-conscious CA, but sounds like you'd end up w/ a bunch of unrepairable lacework after a dunk, and they're not real cheap either
#1 look around and find a restoreable California truck of the same year and model, which will be relatively rust free, and which would cost you less than restoring 2 of those Cinncinatti fenders at Randy's
#2 figure out the reality of restoration so you have an understanding of the difference between buying a good replacement part and building your own replacement part by spending twice as much cleaning and patching a totally trashed old one, which when done will not be the original fender
#3 learn to do the work yourself, as you sound like this may be a "labor of love" and time isn't the important part - then your truck will have real soul
#4 if you really have to have that truck, can't do it yourself, and you have more dollars than sense, find a place that has reasonable rates and isn't so impressed w/ themselves that they don't want to do actual body work - and make sure you have 30,000 in the bank w/ a good line of credit - restoration of a "very rusty" truck will not be cheap, nor will you ever get "good value for your money"
Bill