I used to run (8) MRF-492's in my amp mounted in a 1987 Camaro Z28. I used the Hustler High power coils on the fold-over mast. Blew out 105 amp altenators twice, ran second battery in back, 2 guage wire to the front battery. 500 watts is not too bad but still I don't recommend you key up when you are at an idle. You will fry the altenator. Would be best if you can run external diodes and a 300 amp altenator like they use in Ambulances. Be careful on 40 meters, I hear if things are not right you can deploy an airbag. PS> fun as hell to bust through a pile up of big guns while in your mobile and get a 20db over S9 report from the DX station. When you do make sure you toot the horn to let everyone know your mobile!!