Originally Posted by 89white GT
So what about my transmission? Do you think it will hold. And so think the bottom end is safe if I run like maximum of 12 psi
Transmission - No, probably not. Depends on the HP you develop.
Remember most of the 5.0 transmissions were designed for around 300 HP. Some a little more and some a little less. If you throw an extra 100 HP or more on them, they are going to fail.
Engine - No, not without some upgrades.
For 12 PSI you should start looking at replacing the rotating assembly with all forged pieces, adding a main & valley girdle and above all be very conscientious about keeping it tuned properly.
You can usually get by with 6-8 PSI on stock components.