The crank firing layout will determine how much counterweight you will need. There are several ways to time the firing and this affects crank design. I have no clue where to find the formula but you absolutely need to include this in your planning if you expect success.
I'd pick the smoothest layout and try to reduce mass as much as possible for quick response and snappy revving.
Google the different V-8 styles for some idea how this parameter affects engine power and useability.
Be sure to check out flat crank v8's with 180 degree headers.
The sound will make you howl at the moon.
Or this: https://www.youtube.com/watch?v=DcMtMdFYHyM
If more is better, then too much is just enough.
If you can't afford it, build it yourself.