IF I were in your shoes....
Call Joe at Denbeste Motorsports/Shelby Engine Company, have him build up the whole bottom end. He'll get the rods, he'll get the pistons, he'll get the crank. As long as you're going with the Shelby block, may as well keep that stuff under one roof. They'll do all the prep work on the block and you'll be ready to go.
We did this 5-6 years back with our drag car engine. Called just to buy a block and ended up having them do the bottom end. After you source the rods, source the pistons, source the crank, find a local machine shop to do all the final prep work etc etc..... I think you'll find it's faster/cheaper/less brain damage to have Joe do it.
I'm headed to the shop tomorrow to do some bead blasting, I'll try and pull the Shelby SOHC block off the rack and get you some pictures of what they look like. Give you some motorvation.