Fabricating/Welding Exhaust

Butt welding is fine, just harder to do. Slip fit allows for a little "wiggle room" where with a butt weld, the part has to be a perfect fit(almost).

Sorry to hi-jack: This is the tread I was just about to post... sort of. I have the exact same setup; Heddman shorties, AOD issue, with the Flowmaster over the axle tailpipes. I was going to try and do it myself but I called around for a good shop and they said ~$350 for the install with custom H pipe to fit around the power steering, and they will fit the exhaust up into the tunnel above the lower seat pan plate. (its a convert.)

I was going to ask what to watch for on the quality inspection?

I think I might try to do this myself. I just found out how much the flatbed tow will be; yikes. I could buy all the parts for less than half of the tow itself. Hummmm?

I am pretty good at welding... decision made... it can't be all that tough

i also have the hedman shorties, and 'flow tailpipes, and i fabed everything up myself. if you raise the tailpipes high enough, they will hit the valance in the right spot for the gt exit. you do, however need the gt hangers at the rear. the L shaped straps that go between the isolators and the clamps will need to be made up on the spot. (i used 1/8 by 1/2 inch flat stock)

weld your own exhaust system

I have a built 1968 4V 302 in my 71 early Bronco and butt welded everything at home using a Harbor Freight 100Amp TIG welder ($140 new). I drive serious offraod a lot and bounce around even more. They have held up just fine. One reason I like to butt weld is that there is no metal on the inside of the pipe, so it is better for flow with a consistant I.D. (inside diameter).
I called Flowmaster and told them my engine size and the sound level I want (quieter for forests) and they told me the muffler and the size of pipe for my purpose. Back pressure is important for torque, so I went with long headers and a single exhaust (idle to 4000rpm). For racing use a shorty header and larger diameter pipe(2500-6000rpm).
I got the mandrel bent pipe (round throughout bend instead of flattenned) from Summit Racing ($17 ea). They have different diameters and bend radii. I then went to the local muff shop and bought some straight pieces of thick wall tube for about $10. I got several 2-3' long pieces from their scrap piles.

1st: Attach the short flanged pipe to the headers so they will seal properly.
2nd: Work back by adding pieces one at a time. Position the closest bend where it will go, and measure the distance from the end of the flange pipe to the bend.
Then cut the straight piece (leave a little extra length for angles to be cut/adjusted into it with your $18 Harbor Freight 4" cutoff/grinder tool. Hold the piece in place and tack together. The cuts will make a big diff, so be careful and plan ahead. Split the angle on both pieces to be welded together.
3rd: After both sides are done from the collector to the closet bend, continue to add pieces until you get to the muffler. Don't weld to muffler yet (the back half can be pushed into the muffler opening and there is a little play to help align things from front to back.
4th: Start putting together the tailpipe section, and stick it into the muffler exit.
5th: When it is hung in place, check for any pipe touching the driveshaft, under body sheetmetal, or the frame. If all is OK, then you can take it all out of the car and finish the welds all around (except the pipe to muffler in/out). This is because things move around a little whil welding.
6th: Reinstall the complete setup and realign. Then you can weld the muffler In and Outs to the pipes.

If you did it right it should sound sweet.
Good luck and don't touch hot pipe to flip over without welding gloves on.