I have a 1968 falcon futura and I just put a 1991 crown vic police interceptor motor into it and I am trying to hook up an electric fuel pump but all the instructions I found said to get an oil pressure safety switch... I don't really want to get get one... so is there a wire that i can tap into that would work right... like one that has constant power to it while the engine is running?

Its a good idea to run a seperate 12 volt feed to the pump via a relay and fuse. Then the live ignition on wire is connected to the relay for switching purposes only and wont overload the original wiring. To have the pump switch off if the engine stalls for any reason the relay needs to be similar to the one that gas installers use which has a connection and wire to the coil so that if the coil stops then the relay cuts power to the pump even tho the ignition is still on. This is very handy in case of a crash.

Yes, a tachometric relay is what you want.  I got one off ebay for about $30.  It runs off the coil and kills the pump if the engine dies.  It has a built in 3 second delay upon starting so you can prime the fuel pump.
 
Cheap insurance for sure.
 
Cheers,
 
Matt