Whenever I finally get my 401a with the Tow Tech package (NOT the 53A Trailer Tow Package) I'm going to do a thorough inspection with pictures and post here to do my part in providing intel. I'll try to find a part number and take measurements on the radiator, ID the leaf springs, and whatever else we think might be pertinent.
While this opinion is contrary to popular belief, I'm more and more of the opinion that all Tremors are receiving the same major hardware - leaf's, radiator, etc. - and thus have the same tow rating. And, the difference in the packages is more technology-related (wiring, lighting, etc).
I'm over worrying about it and second-guessing my build. But, I'm still curious enough to put a little effort in to find an answer!