55.2-59 long bed to short bed frame question

[Kevin_C]

So I just finished up shortening my long bed to a short bed and took the 9&1/4" out and welded it back up. I was about to start installing the flatout rear brackets and noticed the instructions were for a short bed and have a center line at 36&1/2 from the rear which puts the rear end too far back. when I measure from the front mounting reference hole it appear to be 3" longer. Can someone confirm how much longer the rear frame rails are on a lonebed over a short bed. Also how much needs to be taken out of the rear bed sides. I currently have a 3.5" gap between the fender and the rear piller

[55_truck]

Kevin,
I'm following your build thread because I'll be doing the same thing shortly and shortening a lwb to swb and installing a flatout kit. Did you follow this thread http://67-72chevytrucks.com/vboard/s...hlight=lwb+swb
or the original thread
https://www.jalopyjournal.com/forum/...-frame.319393/

They mention cutting 5" off the rear frame horns, did you do that?

[Kevin_C]

55 I did but 53chop had an extra long bed. Pictures are tuff because of different picture angles. but on short beds it looks like they have .5" clearance and I have 3.5". I emailed Don at flatout as well. I was going to shorten the rails myself using those links but seeing I want to smooth the pockets and ends with a button release I may go full Mar-k pimp mode which is 50% of my purchase price but small in total cost

[mongocanfly]

cant go wrong with mar-k..!!!

[Kevin_C]

still have had no luck finding how much to shorten the rear horns. seems like all the articles are around the extra long bed. Unfortunately this is holding up my IRS install. If anyone has a short bed with the bed off could you take a measurement from the center of the rivet on the rear perch to the end of the frame. Mine currently measures 12.5"

[mr48chev]

I found a pfd of the assembly manual that every TF guy on here needs to download https://www.trifive.com/55-59Assy.pdf But it doesn't have frame measurements like the AD manual does.

You may have to go with the "axle center line needs to be right here" concept. That unless someone has the bare back end of their frame available to take exact measurements.

[Kevin_C]

I hear ya 48chev. All the diagrams I have found only have wheel base. Without having a short bed side and due to the fact that my bed is completely disassembled im not really able to mock up a fender for the center line. Some of the flat out brackets are based on existing holes so I may have to jump around in the instructions. Im hoping with the amount of projects on the forum that someone can measure their rear frame otherwise I may be crawling under a truck at the next car show with a tape-measure ;-)

[Kevin_C]

I spoke to Don and it checks with the other measurements. The rear frame after the suspension on a long bed is 2&7/8ths longer than the short bed.