You're going to dump a fortune in a set of stock cases to get them to work. By the time they're welded and epoxied I'm guessing $1,000+. Billet cases are around $1,800.
The first time you blow up a motor in stock cases you'll destroy them.
I had the crank break in half in my 18DM a few years back. I ran two passes with it broken and it didn't even scuff the cases.
Go with billet and save time and money down the road.