Numerous questions!!!

I replaced both my inner fenders on my 383 GTS.I dont think you can do this wiyh the engine in.The best way to do it is to scuff were you think there may be a spot weld.When you scuff it with sand paper the weld will show up much better.Then take a center punch and punch it in the middle of the weld.Then drill out with your spot weld remover bit.You do not need to drill to deep.By using a center punch and drilling slow to medium you will not go to deep and you will break less cutters.Some times I could drill 20 welds before I would break a cutter.I then would change the cutter and then break two cutters on five welds at times.Also some of the spot welds may have a burr.Make sure and grind off the burr before you drill.This will help save cutters also.On your shock area there are welds down low also.Your frame will not bend or break when you remove a inner fender.Unless it is swiss cheese.Just take your time and be patient.If you get frustrated walk away for a while.I screwed my new inner fenders in with 3 or 4 screws first.Make sure evrything lines up.Then if every thing looks good start welding.It is not really hard just takes patients.
Jim