Slick 60's

The frame I am working with appears to be a hybrid, later model 70's rear section(~37.5" wide) with an older front 4x4 section. When removing the cab I noticed the rear cab supports had extra bushings to raise the rear of the cab. This was evidently to get the cab to align with the bed, which sat on metal square tubing or wood blocks to get the elevation needed to clear the rear frame arch and rear frame reinforcements that flared upward. I have started some major surgery and removed the top portion of the rear frame arch, so the bed will sit lower and flat and I can remove the extra cab bushings. Pictures follow of what I have done so far, also filled several holes in the frame. My question is how to best reinforce the now thin arch over the rear axle. Should I add vertical bracing below the new top rail, X bracing, bridge the lower portion of the arch, just box this area, or a combination of these, and how far should the reinforcement extend on either side to tie into the factory frame at its deepest point? I plan to use the truck and want it as strong as possible.

Upper arch just cut but still in place.


New upper flat rail.


Frame holes filled.


View from inside of frame.


Lengthwise photo showing a more flat top rail, not completely flat, but rear cross member keeps the last small bump in place.

FarmMotorSports wrote:In my humble opinion, boxing the altered area should provide all the strength needed .
If you're planing on some serious abuse, you can use an L shape doubler on the outside of the frame, Between spring perches. It would be over kill for most street driven trucks.

I'm going to second farmmotorsoorts opinion. I would box wide enough to get near one of the cross members and call it good. As long as the flanges are in good shape I think it will be strong enough.

Nic

I would agree the others. I'm not sure what the Icar standards would be but when you consider that when a crown vic front end is used you drill two pretty good sized holes for the bolts on each side and use plates to box the frame. There's a lot more stress on that section of the frame than there is back there.

Thank you for the help.

Will get going this weekend.