I need some serious help on how to go about this:

Starter bolt hole closer to engine is stripped completely of threads resulting in grinding on startup and truck has sat for a very long while [months]. It was heli coiled before and that helped for a while but it started grinding again so the flex-plate is probably bad too (haven't checked). Another thing is the starter bolt hole is only an inch deep and the other is 1.5 inches deep. Is that correct?

Is there a way to fix it? I'm thinking of taking engine out and rebuilding it completely but I don't want to if that starter bolt hole is toast.