Since OP has zeroed in on a few concerns, such as using what he has, a 318, and the cost savings there of, in lieu of various other suggestions, true costs usually take into account final market value when completed, and eventually offered for sale, or parted, so, how much demand/market is out there for 300-400hp used 318's?
Reality check, that half the population is smarter then 50% of the people and it's a constantly contested fact.
