That shouldn't be a problem.I'm running a Deck,150 watt amp and have no problems.
The starter shouldn't be pulling anything once the truck is running.
Does the truck run with the stereo off?
Where are you getting power for the stereo?
And is there power to the coil/dizzy the entire time?
Someone holding a probe tester on the positive side of the coil while th truck is running will answer the last question
