Pull all of the spark plugs, push all of the pistons down (up) in the bores until the rod bolts don't get in the way too much, make sure to put tubing or hose or tape on the rod bolts, get a helper, and lay the crank in carefully - the helper can move the rods to clear the throws where needed. Then carefully pull each rod up to the throw, and put the caps on, check clearances, etc.. That's what I have done in the past. It's sort of a pain; much easier if the pistons are out.