As far as I understand, the SPF is offered only as a "Turnkey minus" product. That means that it comes without the drivetrain, perhaps a few other minor items. Most SPF buyers have been opting to have theirs professionally finished, but if I'm not mistaken there is at least one SPF owner on the forum who is finishing his himself. Hopefully he'll chime in with more info.
As to comparison to the RCR, they seem to be two very different animals. If you want authenticity in the tub, the SPF claims that a large percentage of parts interchange with original GT40's. If you want to build your own, IMHO the RCR would be the better choice.
Doug