Was the crank turned at a machine shop, or checked for size and out-of-round by you?
If so, I would put the rings on the pistons and install them in the block. If you do it as you are suggesting, you are doubling the chance of nicking the rod journals with the rod cap bolt ends as you install the pistons.
When checking the rod bearing clearance, you put the plasti-gauge between the cap and the rod journal, torque them down, remove the caps and measure how wide the plasti-gauge squished. Easy as pie.
Carl
