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I was a commercial car body sandblaster for 25 years.
No heat in sandblasting.
If there is any, the air stream cancels it out.
I have sandblasted intensely on one side of a sheet of steel and held an IR gun on the other side.
No extra heat at all.
Sandblasting stretches metal.
The trick is to not over stretch the panel, but let it relax down to its normal state.
Take a piece of flat sheet steel and see how far you can bend it before it overbends and work hardens and does not spring back, the same with sandblasting, work the panel to no more than the work harden.
Of course I was doing it for a living , so I was using 175 CFM and a 5/16 nozzle and 100 PSI.
With a lesser blaster or any of the toys from HF, you will never damage a panel even if you tried.
When I hear of 40 PSI and a 1/8 nozzle I laugh, a guy would take all day to do just a single panel.
Never ever sandblast a slightly concave surface, although old fords are pretty strong and will probably survive a concave stretch inwards.
And never ever sandblast over any internal reinforcing ribs or through holes on to the outside skin from inside.
The suck in concave stretch will look exactly like it was blown inwards from the outside.