Networking in an Old House
Unshielded twisted pair will perform fine along side 120V 60Hz wiring.  Don't bother with shielded, it won't pull as easily and is more expensive and isn't needed for you.  Twisted Pair will not have problems because of differential signaling.  Plus you're only talking about 70-80 foot run,  you could still run CAT 5e and get Gigabit.  I'd be surprised if you see a single error on the interface.  Modern Ethernet is amazingly resilient.  This isn't like Thinnet, tokenring, or old coax days.

I'm not saying its to code, but you don't need to worry about EMI at least.

UTP Cabling and the Effects of EMI