Cant get it to turn over

We have run into a bit of a problem. The car won't turn over at all now. We can't figure out why. We know the battery , starter , and starter relay work. We have connected (at least what we think is) all the wires for it to be able to turn over. Some of the wiring is mixed stock (inline six) and some is new V8 wiring. Could this be a reason it is not turning over? A lot of the dash wires are not connected too, but the ignition wiring is . Any thoughts or hints on why it isn't turning over and how to fix that?