In short, by the time you spend the money on an overhaul and all that jazz, the only difference between building a 318 and a 360 ends up being the price of the core motor, and a core 360 is what, $50.00 more than a 318? Pistons, rings, bearings, machine work, etc. are all pretty much the same price for a 318/360. So when the project is finished and you're comparing hp/tq - $$ spent, I think already having the 318 laying around is going to have proven to be a false savings.