Wheelkid,
First, though you did not mention being new here, welcome to CHR. We look forward to hearing about your projects and seeing what you're working on as time goes by.
On balancing, it sounds to me like you're focused on the balancing of the reciprocating weight - the pistons, pins & rings, but not really considering the rotating weight and the dynamic balance. From my limited knowledge on the subject, the basic balance is three pieces - the reciprocating weight; the rotating weight or "bob weight"; and the oil weight, assumed to be 4 grams. Here's a link to a Ford Muscle overview that I found quite helpful in understanding the process - Engine Balancing and Crankshaft Balancing - FordMuscle
After the engine is balanced the flywheel, clutch & pressure plate are generally balanced, too, so that the entire assembly is considered. Once that process is complete, if you have to modify things later then you are working from a balanced starting point, and it's generally not necessary to re-balance the entire assembly - you can simply work from the base numbers, and modify your replacement parts to match, like changing out a piston you can match the weight of the one removed, as close as possible. No one is going to argue with you about the distribution of oil being less than perfect, but it's the starting point that's important. If you have a few grams of oil moving around would you rather it be from a very closely balanced base, or is it OK to have it being added to an imbalance of ten, twenty, fifty or more grams that's causing the crank to flex? I'd rather start from a solid dynamically balanced base, giving a much smoother engine. Others who have more experience in this arena may shoot me down on this, which is fine. I love to increase my understanding of these processes!!