Engines I've done w/those same rods and bolts got 45 ft/lbs. Just like any other SBC w/stock 3/8" rod bolts.
You can use the 15 ft/lbs plus 70 degrees if you have access to the tool that shows degrees, I got mine at NAPA. It is kind of bulky so you may need an extension so it clears everything. The final choice is yours as to which method you use.