Take it to a local body shop and get an estimate. Tell them you want new sheet metal welded across the holes.
By "no Bondo" I assume you mean not filling the holes with plastic filler. "Bondo" is a trade name like "Nike" or "Chevrolet" or "DuPont."
When people ask me if my 1971 442 has any "Bondo" in it I tell them truthfully that there is absolutely none. I didn't use "Bondo" as my plastic filler, I used "Cuz" from my local NAPA jobber, and there is some Cuz in it, but no Bondo!
Benji