Hmm, using parts only because you happen to have them is not always a good idea. To build an engine that goes fast, and is fun to drive a long time you need to get the combination of parts correct. SBCs are very forgiving when it comes to running at all. Almost any combination will in fact run. But not always well. Consider your needs and the vehicle weight, set yourself a budget and then shop around for parts you need to achieve your goal. If parts you already have fall into this margin, so much the better. If not, keep them for later and buy other stuff for this engine. Building a motor is such a lot of work you don't want to kick yourself afterwards for saving 100 Bucks somewhere along the line.
But that's just my opinion, as always.
Think about,
Mad