Radio wiring, help for the noob please Options

[tod914]

Just replaced an 80's era blaupunkt cassette radio with a 73 motorolla radio. The 80s radio had two hot wires, one from the battery somewhere, and the other wire going into the fuze box, spliced into the ignigition wire. The 73 radio has only one wire for it.
Which wire should I hook it up to for power, and which would likely cause less damage if for what ever reason something shorts.

Thanks

Tod