Gerst Dominator Series 4 Link

Yes Joe, unfortunately a stock gas tank is pretty much vetoed, there just simply isn't room,on most A bodies, I've tried several designs to get it to fit, the strange thing is, and I have no explanation for, I have a 71 dart, and 71 duster, on the duster, there's almost 3 more inches between the tank and the pumpkin, than on my dart, so while it may squeeze into the duster, it won't on my dart, and I've checked to make sure axle locations are identical, so this was something new to me, and both have 8.75 rear ends, so if anyone knows why that is, I'd love to know! Anyway, as I go on designing, I may make a provision in the crossbar for exhaust, I think it's very feasible to do, unfortunately, with a suspension like this, they just didn't leave much room to work with.

difference in gas tank size perhaps? I'm guessing this is why: From what I found online, theres 3 different gas tanks used from 70 to 76 in a bodies. an 18 gal, a 16 gal and a 16 gal with front vent tube

Dart's have a 111" wheelbase, Dusters have a 108" wheelbase. So as Joe pointed out that's exactly the 3" difference. It's not the tank, it's just the wheelbase of the car.

Not using the stock tank is a pretty big drawback, and I don't even care about not being stock. I'm not a big fan of having the fuel inside the car, regardless of it being in a fuel cell. And the loss of trunk space is a problem. That's actually the biggest issue for me, I use my trunk because I use my car as my daily driver. And since it is a driver I would need a large fuel cell too, anything much less than 16 gallons would be a PITA on long drives.

Still interested in seeing the rest of the installation. I would love to get a measurement from the axle to the back side of the new crossmember though.