Of course you can use the stock frame. There is NO REASON WHAT SO EVER to swap that frame out! ZERO, they are very strong to begin with.
Any frame swap is simply a "money swap", "time swap" or "work swap". They don't save you money, time or work, they only SWAP money, time or work for different money time or work, PERIOD.
My brother used one of those 28ish Chevy frames under his 22 Buick highboy and it worked like a champ, It has 401 Buick nailhead and runs like a scalded dog.
Boxing, is hardly even needed with a 327 if you aren't going to really pump it up or run slicks or something. That 28 Chevy frame isn't like a 28 Ford frame, it is actually pretty strong.