8 singles on a 1973 340
You can get custom made individual stack electronic injection for just about anything these days. I can't remember the name of the company but I saw the ad in National Dragster a little while back.
Casting heads for $300? Well maybe if you work at or own the foundry but machining them is the spendy part.
Personally I think stack injection is the way to go on this, electronic stack injection that is.