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Ok, my 427 is back up and running and I need to fix the rear end. I have a 3.73 12 bolt in it now, but I also have a 4.56 geared Dana 60 that would bolt right in to it.

The engine is a 440cid with big valve 049 heads, Victor Jr intake, 850hp carb, 249/255 @ .050 solid roller with around .700 lift and a 2 inch header with a 3 inch exhaust.

Would you run the 3.73's, or switch to the 4.56's, or recommend something differnt all together? This is with a 28" rear tire. Now Desktop Dyno says max HP should be around 6600rpm making a 4.10 ideal, but this is the real world. Would the 4.56'd be too much? Or the 3.73's not quite enough? Oh yea, it's a 4 speed car with a 2.52 first gear in a street strip car. I'm not worried about fuel milege or high way speed, just when i take a ride, or go to the strip, that it performs to it's potential, thanks.
 

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456 373

Well to tell you the truth I do not know if you will make it to the end of the track with out a top rpm of 6500 RPMs with the 4.56. If your motor can spin safely to 7000 RPM then the 4.56 will give you all the power and torque you can handle.

Where does the major torque band start on the motor? anything above 375 foot lbs.

THe motor for cruise condition need to be in the power band for a good torque cruise and throttle response transition feel.

Jim
 

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I run a close motor set-up (433)with 4.56 gears and a 2.48 first gear 30" slick.I shift at 6,800-6,900 and go into the lights at 7,000-7,100 with my 8" convert that has a lot of passes on it:D hope this helps.Have you ever had that dana in the car ??
 

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I know you said that you don't care about highway speed but unless you plan to trailer the car to the track and never drive it on the highway or have an overdrive transmission, I'd stick with the 3.73:1 gears. It will be plenty-fast at the strip and you'll still be able to drive it on the street. I used to run 4.56s in my my 70 SS 396 4-speed Chevelle and hated them on the street. Made the car pretty-much useless on the highway and I really didn't even need 1st gear. I could pull away in 2nd if I wanted to and drive it like a 3-speed.
 

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Id stay with the 3.73 just for a better street gear even though you said your not worried about that but that in my opinion is the perfect street strip gear :yes:
 

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The 410's are probably going to be the best choice, the 456 are steep IMO and need lots of rpm on the top end. The 373 with the 252 1st are the better choice but a 410 and 220 1st will be better at the track.
 
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