Go to
www.mortec.com and
www.nastyz28.com/sbchevy/sblock.html for engine numbers. Pickups got both 2 and 4 bolt mains. Early on the 4 bolts went in bigger trucks, where they were needed due to the high loads incurred at low rpm.
There is actually a growing group of rodders using the 2 bolt engines for performance. I haven't seen the stats, but the 2 bolt is supposed to be superior for a high performance street engine. My buddy is building a 2 bolt 400 inch with around 500 ponies.
