Blows Main Fuse at 1/4 Throttle???

Check for exhaust hitting wires underneath the car, unless solid mounted, maybe electric fuel pump wires?

Otherwise pull it into the shop turn off the lights, fire it up, and by hand rev it up and watch the alternator for sparking.
Then check main feeds for tightness on alt gauge posts and strand spots.

and you can check for voltage between the ground post and cable, or is it + post and cable? well' you'll figure it out, I have faith.lol