Where is your starter located? Most likely it will be a 168-tooth flexplate. If you are using a mini-starter mounted to the block in the factory location, some mini-starters have two sets of holes, allowing the use of 153-tooth flexplates. Which one you choose is primarily dictated by how/where your starter is mounted.
Any SBC and BBC flywheel or flexplate for a two-piece seal crankshaft will physically bolt on. Just be advised that the external balance flywheels/flexplates have different balance weights between SBC and BBC.
As far as the Mark IV Scat crankshaft, the only difference is the material and the design of the counter weights. Since you know that your engine is internally balanced, that's a done deal.
Hope this is the info you are looking for.
Cheers
Joe
