installing mustang fuel tank & flipping the rear shackle

[nikwho]

Ok, I bought a '69 18 gallon mustang fuel tank. it's too wide to fit between the frame rails but not by so much that I can not make it fit with a little trimming of the inside of the frame rails. I took out the large cross member that went side-to-side between the two shackles to make room for the tank. It was molested pretty badly so I trashed it and will make a new cross member. There is a ton of flex in those frame rails without that cross member there. Have you guys been happy with simply installing a new cross member at the very rear of frame behind the fuel tank? It seems that it will still flex a lot with the movement of the suspension. Also, I intend to flip the rear shackle hanger. I have also flipped the rear axle and removed two or three of the eight or nine leafs out of the 3/4 ton leaf pack to soften her up a bit. I'd be interested to hear if guys have had problems with their frame twisting or flexing without the cross member going straight between the two shackle hangers.
Thanks, Nik

[Maximus]

I did the EXACT same thing in my '55 2nd series,
Trimmed the inner frame about 1/2" and put a mustang tank in, relocated te cross member to behind the tank and flipped the shackles, and removed some of the springs out of the pack, Unfortunatly that was 4 years ago and I'm just getting the truck on the road so I don't know how it rides....
The only thing I did t really finish is the gas filler neck. I don't have a bed floor in so I just have the filler neck floating above the tank for now...
The install was easy after cutting the frame, and the rivets were annoying on the shackles but it REALLY lowered the ride height of the rear. I also installed a 78 firebird rear on top of the springs so the truck rides really low

Sorry I don't have more insight on how it will operate but it was so weird that you are doing the same thing I did I had to post...
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