I'm starting fitting today, so I'll try to add a little more detail for those that are interested. Tubs are 20swg Pete, not going to be that easy to weld I imagine.
First job is to make a template of the end of the new tub, I used 5mm plywood to give me a stable datum to work from.
Offer up the template to the chassis rail and clamp it in position. I had to notch the brace under the parcel shelf a knat's to get it high enough. If you are keeping the stock tank, fit the filler tube to be sure it clears, on an A body it's very tight to the tub.
Once you are happy you've got it where you want it, I drill through to the rail in 3 places and use cleco pins to hold the template in place, self tappers would do the same job. This ensures you can take it out and put it back in exactly the same place.
You can then use an adjustable square to work around the circumference of the template to mark your final cuts to the bodywork.
Remove the template and clamp to the tub, drill through your 3 cleco holes, trim the bodywork as needed.
Trimming back the end of the inner sill is a bit of a git as you can't get access for a power tool. I had to resort to cutting through by hand with a pad saw, very slow work, took me a good 45 mins.
Sorry for the poor quality pictures, I'll take my camera for tomorrows thrilling instalment....
Very interesting you is one clever bugger Blue. It would scare me poo poo less cutting a car about like that. You just don't appreciate the work involved when you look at a tubbed car.
Petty Roadrunner 416 Stroker 4 Speed
*MMA-609*
"Built to be driven!"
Next job is to block off the ends of the sills with a flat panel. To determine the shape of the rear quarter needs some careful measuring. Mark off the circumference of your template in 1" increments. Clamp the template to the tub and mark that the same.
Fit your template to the car and measure across to the quarter at each mark, getting your trusty assistant (or in my case Jem) to mark the tub as you go. Once you've made all the 40 odd measurements, join all the marks together on the tub and thats the shape you need to cut to. Aim for about 1/8" gap on your final cut to allow the Tiger seal to do it's thing when it's time to bond it in.
You can now trial fit the tub. There's a bit of a knack to getting it in the car past the wheel arch lip. You have to start at the front high up and sort of rotate it in, it will go about 3/4 of the way in and then the back edge will jam against the lip, you can carefully bend the tub to get it past, getting it out again usually involves swearing and jammed fingers. If you are lucky you will be able to line it up with the holes you drilled for your template, usually it will be too tight against the quarter in a few places to get it into it's correct position. Mark the tight spots, remove, trim, refit. Repeat until it fits. The tub will overhang the chassis rail in the middle, so mark that, and if it hangs too far below the floor back and front, mark that too. Remove and trim. I normally cut an inch higher around the chassis rail, and leave an inch of tub below the floor, for no other reason than I think it looks neater that way. You can now fit the tub and tack it in place. The last picture shows to tub in place ready to be tacked. You can see where it's shape differs from the original by the gap at the side panel, I'll make filler pieces here, and also to rejoin the roof bracing that fits to the tub under the parcel shelf.