[PNJSNAK]

Just a suggestion on the sidepipe mounts. I made a bracket that is welded to the side of the pipes from 1 x 1 angle iron. Then I used a piece of 1/8 x 1 flat stock that is bolted to the frame. Weld the angle iron to the side pipes before you Jet coat them. When bolting the side pipe to the frame mounting bracket use a rubber washer between the brackets as a vibration absorber.
When the motor torques, things can not be rigid, or something will break or crack.
Position the body on the frame first with the gasket material on the frame rails, before you make any cuts in the body for side pipes or roll bars. Once you positioned the body to your satisfaction with the car on intended wheels and drive train installed. Drill a couple (4) pilot holes where you can put a couple of the large rivets (4) as location dowels.
Then you can begin to measure where you need to make cuts (Oh Boy!) in the body for the side pipes, roll bars, bumpers or quick jacks, etc.
When doing the roll bar be very careful deciding where to put the holes. The manual has approx layout positions for the holes, but watch out where the interior rear wall is. You don't want to run your roll bar thru it. The roll bar mounting brackets may need to be modified or spaced with spacers.
It's all part of the fun.
Always remember, plan your next move, make a decision, then go back and rethink the decision, then check things at least twice before you do it.
Remember "The Manual" is only a guide you are building a car that is not produced like an assembly line in a factory.
There is lot's of help here.
Good Luck.
Jim