I've done a LOT of prep work for a bottom mount twin scroll single. I was really drooling over ACF, but the guy is a ghost. There are other options coming to light for me, but I'd venture a guess that I have spent close to $6k for foundational mods to get ready for a single. Now add in the cost of a single, and I'll still need to add on the install components. Exhaust mainfold studs, gaskets, odds and ends that nickle and dime you to death. I'll guess that there's an easy $500-1000 of oddities that I'll need to get on top of the kit itself.
Going fast isn't cheap.