The 3.09 first gear set up is cool, however you will probably break it! Its not very strong. I know as I put a NOS set in my Cuda years ago. Had a 475 HP small block with a 3.55 rear. Ran good fora while then nocked lotsa teeth off on Woodward one night. Drive the regular 23 spline until you can swap trans. 18 spline will hold up better but bigger budget needed. Tremec trans don't shift under real acceleration unless heavily modifyed so don't waste your money there either. They break too. Cut the friggin floor and put a Richmond in. You only have to mod the left side of tunnel and move the crossmember. Big job but It will make you smile.