Tim,
If you decide to look into a flathead do yourself a favor and give the guys at H&H Flatheads a call. They are the go-to guys who've been doing flatheads forever, know all the old school lessons, and know how to apply them to give you a reliable flatty engine in whatever configuration you want - HNH Flatheads: Ford Flathead rebuilding specialist Flatheads are super cool, but when you look at the $/HP be ready for sticker shock, especially if you start pushing the power envelope.