I have a lifted 89 Suburban that I am swapping a built 454 into it and I don’t know what automatic transmission I would want to put in it the engine will make 550 horsepower and it’ll be a mudding rig thank you for any advice you have!

 

HP doesn't matter. Pick a tranny that's rated to handle your torque

mechanical:
beefed up TH340/400

electronic:
4L80/85