AA rock box crossmember

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Oct 18, 2004
West Georgia
i'm nearing the end of a long modification to my '74 fj40 redoing pretty much everything on the truck. my last major concern is that i've got a AA rock box mated between a sm420 and LC 3 speed transfer case, i've also got a sbc, i have the AA propeller crossmember bolted to the back of the transfer case, but i badly want to fab some kind of crossmember to go about halfway between all this stuff, preferably to the rock box. has anyone else out there come up with anything like this? i'm worried about flex in the middle and also if i roll that it might break right there. any pics or suggestions would be awesome, thanks!
i just got done fabbing my crossmember tonight. I have a LT1 4l60e 3spd combo, which is way long. I used the AA adapter as my mounting point. It has 2 threaded holes on the bottom. All i did was take some angle iron bolted to the frame rails, then made a crossbar from some rect. tube and used a GM mount ontop if it. then i skinned the whole thing with 3/16 plate. Very similiar to a jeep style crossmember/skid. The aa propeller style always seemed goofy to me.
i would like to hear more detail or see pics of how you attached the crossmember to the rockbox, and what type of gm mounts did you use?
I've been running a sbc-sm420-AA adapter-3spd tcase in my 40 for a few years and I haven't noticed any problems. I would think the rock box would be as strong or stronger than the adapter.

I'd be interested to see what you come up with.
My crossmember hangs down low, but i trimmed the floor a little and stuffed the t-case up all the way. I would have to have done a body lift and i am already in the soa process and don't want any more lift. So, it hangs below the frame 3.5".
here is the link. the first two are of the original that i did which was way low.

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