I've just finished building my bike.
I purchased a new Gunnar frame and then added components off my Fuji.
I have a mixture of Tiagra & Untegra components.
When you take parts of another bike, the cost comes WAY down.
I did have to order a new FD and long reach brakes. Everything else ported over perfectly. The parts that I didn't have to buy: RD, seat post, handlebars, cables, crank, cassette, chain, wheels/tires & pedals.