[72sbc427]

I started with a 273 gear and went to the 410. The 273s were spin happy occasionally even on the freeway. No issues when I went to 410s. But it wasn't the gear size that made the difference. Rather it was going from a warn out limited slip and going to a good posi unit. 410s were definetly annoying on the freeway though until I put in the 6-speed to bring the rpms down. If 273s meet your primary need then stick with them.

 

[72sbc427]

Wow, my post explaining the experience of having both 410 and 273 gears in the same car got completely ignored.

pwrjunkie80 - are you currently running a posi unit in the rear end that is in good shape? One wheel wonder rears will definetly cause what you described. Going from that to posi made a big traction difference on both launches and freeway. Changing the gear size only changed the from power from high speed to low speed. This was with 450hp, 28" tall tires, and well built th400. The reason I ask about the posi is because you made mention it wanting to spin out on you, like the right rear tire doing all the spinning would. With both wheels together you are sure to still break tires lose with 660hp, but should be fairly controlled and semi straight. I have seen many 273 rear ends that could not hook, including my own. All do to being the original tired setup and not so much as even a rebuilt rearend. Also going with a rear swaybar and boxed control arms made the rearend more predictable and controlled.

 

[72sbc427]

Sounds like you are just having the same problem as any one of us.........we need more money!!! LOL

I'm sure that new motor was indeed not cheap at all. But 660hp?? Hell Yeah! Sounds like you have the power part of the project taken care of :hurray: I should be right up there with ya at around 700hp in the next week with the completion of a turbo install :beers:
You could just give up on the convensional way of thinking of a car going straight down the road and see how well driving it sideways works