Try 1 of these kits, found on the Jegs web site, they both prevent "run on" when the master disconnect switch is turned off. I would recommend the the 250 amp one that I used.
Charging System Shutdown Relay KitP/N - 764-50103
Alternator feedback can keep your engine running even with the master disconnect turned off - this kit eliminates engine run-on. Highly recommended by most racing sanctioning bodies. Easy to install with all hardware and instructions. 35 amp maximum
Note: For racing use only.
I used this kit in my car:
# High Amp Alternator Shut Down Relay KitP/N - 764-50105
This kit, comes complete with 250 amp solenoid and two 10' sections of 8 gauge wire, will effectively handle alternator feedback of the highest amperage alternators. Eliminates engine run-on when the master disconnect is turned off.
You should also buy the battery relocation kit and a Master cut off switch. The kit will have enough wire to run up to the starter and all the other crap you will need. Good Luck!!