One of the top tools in my inventory is an industrial soda blaster. The thing requires me to rent a diesel pull behind air compressor to run it. But I had a 69 cj-5 where both fenders were screwed down to the tub bondo'd under and over the (roof flashing) then bondo'd over that and it was over 1/2 an inch in places.
The soda blaster tore though the bondo removing mil upon mil without causing any more damage.
There are low cost/capacity ones out through eastwood or harbor freight that work good they just take a bit longer to get the job done.
The end of the day though your only removing the junk leaving the good stuff to patch with using a soda blaster. Using a grinder or even wire wheel your going to tear into stuff you do not want or your going to be there all day covered in dust. Break out a soda blaster and shoot the area standing there and then wash the car off and bam your done.
Almost every part of that car can be hit with a soda blaster(the interior not so much). You will find it is a great tool to have in the shop. If you have encountered this type of spot there is no doubt other questionable repairs.
The thing will pay for itself in cleaning areas like the front suspension where you can shoot right over the rubber removing layers of grease and muck before tearing down the suspension. Have rusted rotors? That's a quick and easy fix.
Here is a fun one. Have body mounts bolts(or any other bolt) that are covered in a caked layer of rust on the threads? Before you break out the torch and fry your rubber bushings. Hit the bolts with a soda blaster and watch the threads revel them selfs enough for you to remove the bolts saving the bushings and not heating up the floor.
The tool is one of those things you will find you have reason upon reason to use it once you have it. If you have a air compressor up to the task then spending hours with a wire wheel, sanding, or grinding will seem not as good. I have been there and would not go back unless I was being paid to do so.
Heck I just did 2 truck racks for my boss on Monday and Tuesday for the new trucks they have coming in. It took me and another person 4 hours with a wire wheel to prep each one down to bare metal with many uneven surfaces and layers of paint. The whole time I am thinking If I just had the blaster it would have been an hour each (just me) tops to prep them down to metal. But, I am getting paid to do it there way.
The soda blaster pays dividends once you start finding all the things you can use it on. On a project like yours your going to find that it will come in handy in many situations saving you a great deal of time and pain.