installed new starter and now I have a short?

Many of those mini-starters come with what you might call a bracket which extends the terminals. This actually comes OFF and reveals more common looking studs right on the solenoid. It might be that adapter bracket is hitting the block.

This idea of installing high current cables "blind" is not good. Get under the car, get lights, get a mirror, get whatever it takes to get under there and LOOK.