dont use the power seats or rear defoger
Well I have not used that product but 50 amps is 50 amps right? On my cars that have the same draws but with a 30 amp draw with my 7al3 that will draw more than your interior lights minus your high beams. You should be fine as long as you are spinning the alternator to get full output when your loads are on. On my east coast one wire I had to spin the 1" driven with a 4" drive to have sufficient voltage below 4000RPM, yours may require a 5" drive pulley? You need to test the voltage at various rpms with full electrical loads on it and find out if you are spinning it fast enough for your street driving.
If all else fails you may choose to check the directions and see what there rpm preferences are for there product to be sure you do not over rpm it if it is a cheap POS, you just never know until you do sometimes.
Bruce