Hey there, fftoddster, I would also be a little skeptical about the 4" drop they claim. I also have a '37 Ford sedan. My rear end mounting kit is pieced together with some TCI non-parabolic springs I bought from a guy on craigslist and the front & rear spring mounting brackets came from a streetrod shop in Orange Co that went out of business. I also got a rear sway bar from them. The rear spring shackles go thru the frame rails becuause it seemed certain the kind that mount like TCI's version wouldn't get it as low as I wanted. Even with the ones I got, I still need a 1 or 2" lowering block.
I c-notched over the axle because the axle would definitely bottom out on the bumpstop if anyone was in the back seat.