Ideas on what's causing my click/tick/rattle noise?

One other thing I would check is the bearing clearance. Is the crank std size, or has it been turned? If the crank has been turned (some time in the past, such as .010 under) and standard size bearings were used, it would lead to excessive clearance. Have the crank micked, and look at the back of the bearings. They should be marked as to what size they are. It is rare but I have seen the incorrect size bearings in a box. I always double check with plastic gauge.
(the ideal way is to install the bearing in the rods, and measure with a dial bore gauge, or inside mic, and compare to the crank journal measurement, to determine the oil clearance)