Thanks Mike. It took me a while to find a big enough container but believe it or not I finally found a 21 quart stock pot at Walmart for $22 that was just big enough to handle the whole latch assembly. It has a ceramic type finish which is important since you don't want to use a container that will wind up being coated with the phosphating solution (e.g. galvanized steel or aluminum). With a container this size just be prepared for a long heat up time (about 30 minutes) to bring it up to the proper phosphating temperature (approx. 200 degrees F). http://www.walmart.com/ip/Granite-Ware-21-qt-Stock-Pot-with-Lid/17165786
I used the Palmetto zinc phosphate solution on the assembly which gives it the proper gray appearance. For the two springs located on each side of the assembly I used the Palmetto manganese phosphate solution which results in a more darker finish, almost black in appearance. I'll try to snap a few pictures tomorrow to show you the end result.
Now if I can only find a big enough container to phosphate the hood spring assembly I'll be a happy guy.