I put an LS1 rear end on the Formula the other day with 3.73 gears. It doesn't stick out too bad with the stock GTA wheels.
The gears made a vast improvement over the stock 3.23 gears, as well as the LCA Relocation brackets.
I just need to put the calipers and new brake lines on soon, I don't feel that safe driving with only front brakes.
Also need to do something about the speedo since it's reading quite high.

Here are a few pics,

 

Good looking ride. polish your taillights, though.

 

thanks.
The lights are polished, they just have dust all over them.

 

i'm was also contemplating the ls1 rear swap. it loooks like it doesn't stick out as much as i had orginally thought. great pics btw. i believe i will do the swap as soon as i get some stuff out of the way.

 

If thats as much as they stick out then I may do that for my car later on instead of rebuilding my 9-bolt with PBR calipers.

The only reason I'm reluctant to swap is because I like the light weight of the 9bolt, and I love the PBR rear brakes. But with an LS1 disc rear end I can get the brakes at least, and a decent posi that can be rebuilt much cheaper than a 9-bolt.

 

anyone know what kind of power (torq) an LS1 rear end can handle??? I got a line on one the other day and I was a little curious about how strong they are since I was originally planning on a Ford 9 incher.

 

They are weak since they are pretty much the same as the ones in our cars., just a bit wider with newer brakes.
Get the 9".