What do I do next?

If you stay on the original post, the person you were talking to will know your asking another question. If you make a new post, they won't know, except by accident.

Does it blow at key on or crank position? Maybe a wiring circuit is shorted? Can you turn the crank by hand, the engine isn't froze-up?

The ignition switch has more than one position. The crank position is spring loaded will spring back to on position when released. Does it blow at the on or crank position? Just trying to understand? What is the amp rating of fuse? Again can you turn the crank by hand, try to turn the flywheel if no other way.

If the engine is froze-up, it may be causing the fuse to blow? That's why I asked if you could turn the crank/flywheel by hand. If you can turn it, the engine isn't froze.

Pull the starter relay, Use jumper wire from battery to proper terminal at the relay to crank, don't use ignition switch to crank, key on. Does the fuse still blow? Your going to have to do some testing, the only way. Any testing, make sure the tranny is in park or neutral and the e-brake is set.

Ras was the original person you were talking to, maybe he can give you a better answer. He is higher rated than I.

Glad you go it going your way.