Pretty amazing how a good looking (from 50 ft anyway) restoration hides so much rust damage.
I wouldn't depend on fender mounting holes to position the outer cowl panel. Those can be redrilled if needed. The critical thing is door gaps. If you have the hinge pillar welded to the rocker, it may be too late to fix that, although if you find the dimensions too far off, I'd be cutting welds out. The FAM has dimensions from front of firewall to the hinge pillar locations that you should at least check.
