Hooked pulling front wheels then spun

That is very interesting. This set up worked flawlessly when the car was slower and lighter. Now it's 3600 with me in it and running a ton more power than before. I'll definitely take some clamps to drag week to try if needed. I added weight with the procharger, roll cage and Dana 60.
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I went through this same scenario. Put in a bunch of power and everything went to ****. This is what I would suggest if your looking for opinions.

- First. Are you sure your rear end separation isn't excessive? A video would tell. And slow motion really shows what's going on. The more power you throw at it the more the rear wants to separate.

- Check your pinion angle to make sure it is still what
it was. If it has changed, then,

- Do you have your spring perches boxed? If not, check them, make sure they're not flattening out. If you can see any air gap at either end, they're starting to curl and your pinion angle is changing on launch. If good, your lucky but get them boxed if they're not.

- Get some dble adjustable shocks on the front.

What finally got my car to hook was with the rear shock rebound on full tight and front shock rebound added. I ran QA1's on the front with 18 notches and where things settled down was when the fronts were Increased to 7. 7 rebound, 18 compression.

With front shock rebound added my front end rise slowed down, which kept the rear tires planted long enough to get me out further without spinning.
I wouldn't have thought, but it made the difference for me. Front shock rebound can play a big part with leaf springs and lots of power.