Bumpside/Dentside F-100 4x4 frame differences

[JoshT]

My 68 F-100 LWB 4x4 needs a little work on the frame & suspension. Got at least one cross member under the bed that needs replaced for rust and someone in the past relocated the front coil buckets lower on the frame and the buckets are cracking now. All fixable stuff once I find parts. In addition to this I'd eventually like to upgrade to a later model (wider) rear axle, two speed transfer case, and possibly swap spring hangers to run 2.5" leafs for better availability/aftermarket.

Browsing facebook marketplace the other day I came across someone selling a "75" F-150 LWB 4x4 chassis that he was planning to use for 60 body, but project fell through like so many do. Looking at the single picture he posted it's got full suspension, both axles (and tires so it'll roll ), transmission, transfercase, and driveshafts still on the chassis and asking $1000.

One option would be to use this frame for parts to fix/upgrade mine. It appears from the picture that the 75 frame has the same style coil buckets and shock mounts as my 68 frame, but I can't verify this from the picture and Ford part numbers don't agree (no surprise there). I could probably shorten/narrow one of the rear cross members to replace mine. The rear springs and spring hangers would set me up for 2.5" leaf springs, it'll also provide the wider axle once the perches get relocated. It appears to have an FE pattern bellhousing and manual transmission, so best case transmission and transfer case upgrade, worse case spare parts. I guess biggest question here is would would the coil buckets work and is it worth the $1000 for the parts?

The other option would be to use the whole frame under my body. EDIT: Ok after thinking on it a bit more, I hit the Theseus Paradox. How much of the original can be replaced and it still be the original? The answer id different for everybody. Already there’s not a lot of this truck left that is original. The body has been replaced at least twice and most of it needs to be replaced again. The engine has been replaced, but I can’t comment on the rest of the drivetrain. The last major assembly that’s original to the truck is the chassis and I don’t think I want to give that up.

[cep62]

If you're looking for a parts truck the "76-"79 have power steering and front disc brakes , and 31 spline rear axles.
"78-9 have a better tie rod set up.

The cab will bolt to the later frame

The frame gets longer and wider behind the cab , by a couple inches each way.
there are ways to compensate for this and bolt on your older box.

the wider frame accommodates the rear mount gas tank, to get that out of the cab.

[cep62]

"Quote" How much of the original can be replaced and it still be the original? The answer id different for everybody. Already there’s not a lot of this truck left that is original. The body has been replaced at least twice and most of it needs to be replaced again. The engine has been replaced, but I can’t comment on the rest of the drivetrain. The last major assembly that’s original to the truck is the chassis and I don’t think I want to give that up.

In the end it's up to who are you building the truck for ?

If it's you , then build it your way and forget what "they" say .
If you're going to sell it in few years build what sells.

[JoshT]

Thanks for the reply cep62.

This truck has been in my family since before I was born. My dad got it from his step dad when I was still in diapers. I intend to pass it down to my kids/grand-kids if I have them (doubtful at this point), or my nieces and nephews if I don't. Safe to say it's getting built for me and I don't care what they say. That said, if I tried to sell it out of the family I'd probably have to answer to my dad, my sister and a few cousins.

If you're looking for a parts truck the "76-"79 have power steering and front disc brakes , and 31 spline rear axles.
"78-9 have a better tie rod set up.

I'm not looking for a "parts truck", I am looking for parts and this chassis happened to appear local that looks like it might have parts I can use. It's local, but not local enough that I can drop everything and go have a look. Not to mention that 4x4s that age and older are difficult to come by around here at a "parts truck" price.

I've already got 76-79 power steering installed and a front disc conversion. Was 76 the first year for 31 spline 9" in trucks? That would be a plus, but realistically this truck has never broken an axle and I don't intend to haul near the loads that dad used to. If I need to do that he's got a diesel F-250 that would do it better.

Was it 78 when they got the better steering setup? I was thinking it was earlier than that for some reason. IIRC the 75 D44 would still be a stronger axle and could accept the same disc brake conversion I've got installed now.

The cab will bolt to the later frame

The frame gets longer and wider behind the cab , by a couple inches each way.
there are ways to compensate for this and bolt on your older box.

the wider frame accommodates the rear mount gas tank, to get that out of the cab.

I know about the length and width differences from the tech article and was considering that as an option the other day, but I don't think that I want to do it.

If I did frame swap I'd close the bed to cab gap, move the axle 2" forward and shorten the rear frame horns. For the bed, rather than re drilling the mount holes in the floor, I'd make mounting brackets to bolt to the frame and accommodate the stock bed bolt location.

Already planning the gas tank relocation with current frame. Seems that the Mustang tanks work good with the narrow frame. I've also got a 22 gallon Bronco II tank that would fit in there pretty good if I don't use it in the project I bought it for.