FF427C, Call there tech line. Nice to work with and vary Knowledgeable. I will have a picture this weekand.

 

The FF427 headers are for 1953 and newer F100s. Pic and description here:

The Sanderson FF427 header set is designed to fit 1953-Up Ford F100 pickups using the Ford 332-428 FE engines.

There's also a pic of the FF427 in Julie's post #20.

Maybe the FF427C is a different header? There is no FF427C listed on their website.

 

And the '48-52 frame is 2 inches narrower at that area. So if it says '53 and newer, it may mean because it's within an inch of the frame.

 

Yeah we are really talking about one of those things where fractions of inches will make or break! You'll find you will have a few of those with an FE in your Economy Built!

And yes that 1/4 inch I was talking about Scotts measurement is looking like its either 1/4 inch of clearance or 1/4 inch of not enough! If you had one you could just kinda wiggle in there I'd feel alot more comfortable on this call! Remember you have a brake line, fuel line and wiring right there too - so they would have to be moved down. You don't want that fuel line to close to the exhaust - vapor lock!

I was looking at those again as well and it looks like the flange is not pointed straight down but rather has a slight angle to it (like 3-5 degrees). I'm wondering if you could mount them on the opposite sides to get that to tilt forward a little so the pipe would clear the steering box a dash more, then round it back?

 

Check vintage ford in Sacramento. they carry amazing swap stuff. ex.:they carry a single bracket to stuff a Toyota landcruiser powersteering box right in the pocket where the orig was, on my '53 with a 428 & C6, but I used Sanderson headers (Huggers). All fit like a glove! Also, try FE Specialties in Sacramento. Tom is amazing source of ideas, and both companies are very resourceful for weird crap.