I think you're spot on with the progression. I would have to back up on my Swinger. The prev. owner split the single exhaust and made it into duals. I still have the 2 barrel and stock 70-318 under the hood. The closest chassis dyno I know of is a hour and a half away but the local drag strip is only 20 min. May be I should take the ol' girl out for some baseline runs. A performance increase would give me a percentage that could get close to a horsepower number.