2005 chevy avalanche 1500 5.3 4x4S

o I'm a DIYer, I've installed a 5.3 crate motor into my chevy avalanche. Just fired her up today, everything was looking good drive fine but is stalling. I had sent the computer off through mail.order tuner prior to having the motor put in. I am sending the computer back for them to fix it after telling them the truck is stalling when coming to a stop. Anyways I went to start the truck again today to go for another test drive and as soon as I went to turn on the ignition the truck had shut off and the starter was stuck continuously turning the motor over so I had to unplug the battery. I checked the fuses and the ignition fuse was blown I swapped it out for a new one. Tried starting the truck again and nothing the fuse keeps blowing when I go.to.turn the key idk anything about electrical nor where to start if anyone could help.me out it'd be very grateful. Currently pulling my hair out