Picture of the section

As I said it finishes just behind the seats.

 

It's doable for sure, i've seen it done before. Are you sure that the rear half of the car isn't as rusted? Mine had the begginings of what your car has up front (around the tension rod/sway bar brackets on the lower frame rails) but not quite as bad. The majority of my rust was the rear wheel wells, above the gas tank, and the channel at the base of the hatch. All those areas required extensive patching.
With the exception of a few small spots, all of the rust in the front half of my car was taken care of with the sandblaster and grinder.
I should add that either way you have hundreds of hours of work ahead of you, personally i'd probably try to fix the rust before trying to graft on the front half of another car, but thats just me...

 

that new section sitting on the wet looking ground is most likey rust on the bottom by now. you should at liest get it off te ground, you may have two rusty sections there.

so if I follow you right you wana cut the front half of the gold car off and then graftin the front half from that section laying in the weeds? wow that balsy. you will need some pretty good welding skills to do that and to make it as strong as orginal, I would imagine that you would need to brace it and add a crap load of metal to it for that to work.

you still never answered what the floor and the rear half of the gold one looks like.

I would be very very concerned with those rocker panels that are rusting from inside out. Thats the structure for the body and it is probably pretty weak did you take a body hammer and tap around the rust to see how far it has spread???

 

I do not want to graft that piece onto the gold car. I want to remove the bad sections of my car and replace with the good bits from this one. If you read my previous post I stated that the frame was only rusted badly in front of the crossmember (the rest cane be delt with with a wire wheel). I was asking if it made sense to remove from there or replace the frame from under the car come forward.

I intend to keep the original inner fenders, firewall, floor etc.

 

Ah ok I see what you are asking now. Still a lot of work though, you'd have to drill all the spot welds that hold the frame rails to the rest of the car (probably hundreds) and then make sure nothing gets warped in the process. I would still suggest a sandblaster, and see what you have left when the dust settles...

 

The SA may become a parts car, I looked at an FB yesterday and should be picking it up on Monday.

 

WELL GOOD LUCK MAN, THE FB MIGHT BE A BETTER STARTING POINT, i FEW YEARS NEWER AND i WOULD BET THAT MAZDA FIXED SOME OF THE RUST PROBLEMS AS THE YEARS WENT ON.

DO EITHER OF YOUR SA'S HAVE A GLASS SUNROOF??

i NEED ONE

 

No the SA is a hard top.