I've got a '74 Duster I'm working on, and I have a question on a planned change to the trunk floor.

First, the spare tire well was very rusty, so I cut it out. Right now the metal is cut off about an inch down into the well from the main floor pan area. Like this, the metal is pretty flexible when you push on it.

I know that welding in a new spare tire well would fix that, but I have another idea. To get a nice sounding exhaust, I'm going to have a Flowmaster 3 chamber muffler with no more than 2 feet of pipe behind it going to the rear bumper. Obviously, there is no way you're going to fit a Flowmaster in there with the spare tire well intact. I'm going to use a fuel cell, so the gas tank isn't a problem.

I was thinking of welding flat sheet steel over the spare tire well area. But I wonder if the dips and curves in the original spare tire well area contribute to rear body rigidity. And I don't want to give up any body strength. Would this be a problem, or should it be ok to go with the flat steel?

I will cut and bend the flat steel to allow for the dip in the floor of the fuel cell.

I've seen some mod'ed Dusters with the tire well cut out and a flat plate welded into place. For rigidity some people used a thicker gauge of shhetmetal like 20 gauge, and some also added gussets to the metal and frame rail/ some 'hat channel' across the tirewell void...

visit a local sheetmetal shop for this...while paying for this you might as well have them bend up some sub-frame connectors...


-D.Idiot

The thing that can happen to the rear box section of a high HP A-Body is that the box "tails" want to spread apart from each other.

Once the fuel tank and tire well are out of the way, most chassis shops will "tie together" the rear frame rails by adding a new cross piece about 1/2 way between the current ones. (Shock mounting crosspiece and the rear bumper "cap-off" crosspiece) Connect your new piece of flat trunk floor sheetmetal to this new brace and everything ties together for good strength.

OK. That sounds like a good idea. I was thinking of getting a metal shop to roll some channels into the piece of flat sheet steel before it goes in, but it can only have channels in the cut out area (above where the spare tire used to sit).

Connecting the frame rails together in that area is something I hadn't thought of yet.

Tim, if you were going to make a frame for the fuel cell mount, design it to act like a crossmember, this may add enough reinforcement without adding any extra weight. A frame for a rear battery mount could also make an extra crossmember.

Cecil