I locked in to the SL-C because of the design and simplicity of construction. Is is not a replica of anything. My favorites are the 917, then P-4, GT-40 in that order. During my visit with Fran, I almost changed my order to the 917 mono, but decided that it would not make a very practical street car. The SL-C offers a bit easier egress (for my twice broken back) and economy of build as compared to the 917 and P-4. I would not think of building a 917 with something other than a Porsche engine, or the P-4 without something Italian.