on the back of the engine block is a terminal with philips style scews maybe 15 or so. Most likely from radio shack. Is this for positive or ground wireing?

they're used so when you pull the engine out, you dont have to cut the wires or unhook them from every sensor and undo all your fancy loom/zip ties, etc.  its not NECESSARY but more convenient.

you could accomplish the same thing with a plug with as many connections as you need, senders, ignition, etc...