[siggyfreud]

Welcome. Sounds like an awesome place to start and super cool that your wife got you that transmission!

On my project I chose to upgrade the existing 12bolt with better axles. But going to a Ford 9 is also a popular approach. I plan to run 500-650HP depending on the motor I put in. That said, the number of really hard launches it's going to see will be limited (not saying never though) so I'm not extremely worried about the rear holding up.

There are a lot of people running 700hp on a truck 12-bolt and living to tell about it.

I think things to consider to help keep it healthy though are strong axles, a cover that can add some pre-load to the bearing caps, and a good rear suspension setup that will keep the rear from bouncing under power. If you're bouncing it a lot under acceleration, that is where you're going to break something.

But I remember a lot of guys over on hotrodders.com running 600-700 through their truck 12-bolts, with upgrades, and doing fine.