The rear contoured chrome bumper, often referred to as the 'Sport bumper', was an available option on all light-duty Ford trucks starting in 1964 and remained unchanged until the end of the '67-'72 'bumpside' era in 1972.

1964-1972 rear Sport bumper

When these trucks were new, more often than not they were delivered to the dealer without a rear bumper. The only exceptions were if the buyer checked the appropriate boxes on the order form to specifically request either a heavy step-type bumper or the chrome Sport bumper. While these trucks were just starting to  be looked at as a second vehicle, or even primary transportation, a majority were still being purchased to be used as a work vehicle. Since bolt-on frame receiver hitches weren't being used, the customers tended to prefer the heavier step bumper since that would allow them to pull a trailer or camper. Therefore, you typically would not find a truck with a special-ordered chrome Sport bumper.

However, with truck owners fixing up their light-duty trucks in recent years, the Sport bumper has become an extremely popular bolt-on to add a little style. However, until recently the mounting brackets weren't being reproduced, so it became necessary to find an original set (not an easy task) or fabricate new ones. Finally around 2010 the Sport bumper mounting brackets started being reproduced by aftermarket sources, making them readily available to enthusiasts.

1973-1979 rear Sport bumper (w/ 37" frame rail spacing)

When Ford redesigned their F-series trucks in 1973, one of the changes made on many (but not all) models was a widening of the frame rail spacing of the rear half of the truck, from 34" to app. 37". This meant that the rear Sport bumper had to accommodate the change, by relocating the bracket holes several inches outboard on each side. This was great news for 1970's buyers who weren't interested in the big bulky step type bumper...but not so much for today's enthusiasts who want to replace their step bumpers with the more-stylish Sport version, since the '73-'79 truck mounting brackets were even harder to find than the earlier version and weren't (aren't) being reproduced. For years, one of the most commonly-asked questions in the '73-'79 Ford trucks web forums and social media groups is "...will '64-'72 bumper brackets work for '73-'79 trucks?" Nobody could answer that question, since the few people who had a Sport bumper on their '73-'79 truck didn't have a set of '64-'72 brackets to use for comparison, and vice versa....and weren't going to remove their bumpers just to do the comparison anyway.

Well, let's consider this FAQ answered....yes, the readily-available '64-'72 rear Sport bumper mounting brackets can be used to mount the '73-'79 Sport bumper to specific applications with 37" frame rail spacing!

Let's investigate:

	This is a side-by-side comparison of the right rear Sport mounting bracket set between the '64-'72 (left) the '73-'79 (right). As you can see, they are actually very very similar. (Yes, this pic is the equivalent of getting Superman and Batman in the same photo!)
	A side shot shows the overall shape and contours of the frame brackets very similar. Top: '73-'79 Bottom: '64-'72
	LEFT: The '64-'72 frame bracket (top) has a 'kick-up' along the top that the '73-'79 bracket doesn't have. You'll see why in the next photo. RIGHT: The differences are more obvious when the two frame bracket styles are laid on top of each other.
	Top: '64-'72 - Bottom: '73-'79 The 'kick-up' on the '64-'72 frame bracket that isn't present on the later version was needed for clearance for the support arm. Notice how the bracket-to-frame holes on the early frame bracket are aimed upwards (highlighted in yellow), whereas the later re-designed brackets include a redesigned support that's angled differently for clearance. However, while the two support brackets are bent slightly differently, they do start and end in the same place. One could use the '73-'79 support arm with the '64-'72 frame bracket, but not the other way around. The early support cannot be used on the later frame bracket.
	Here is a comparison shot of the support arms between the '64-'72 (top) and the '73-'79.
So...based on the photos above, you can see that the early bumpside brackets CAN be used to mount the Sport bumper on the later dentsides.  In fact, it's ALMOST a bolt-on, but not quite. The frame brackets are secured to the frame with two bolts on each side, but one on each side will not line up, so you'll need to drill a single hole on each side.
	In this example on a '75 2WD with 37" frame rail spacing, one of these bolt holes, the threaded nutsert towards the front of the truck (yellow arrow) can be reused. However, the bolt hole seen lower to the left will not. A new hole will need to be drilled higher up.
	Loosely attach the '64-'72 brackets to your new '73-'79 Sport bumper. Lift the bumper and brackets up and install a bolt on the forward-most bolt hole. Then use a hydraulic floor jack to lift the bumper so it pivots up on that bolt. Once you have the bumper where you feel it needs to be, simply mark the frame on each side where the new hole needs to be drilled, and lower the hydraulic jack and remove the bumper.
	Once the bumper is out of the way, simply drill out the holes as marked (yellow arrow) and you're ready to reinstall the bumper. Just make sure all bolts are installed loosely first before tightening any down tight to allow a little adjustment as/if needed.
NOTES: The threaded nutserts in the '73-'79 F100/250/350 frame require a 9/16"-12 x 1 1/2" long bolt to be used. Just grab four of them from the local hardware store, along with matching locknuts and washers.