Hey everyone, i'm in the midst of a 1973 Dodge Dart Swinger restoration. I am putting a 360 in it and was just wondering what is the best trans and differential for street/strip performance. ill be putting everything from Edelbrock on the engine 750 cfm carb, performer RPM intake, heads ect. ect..., hoping to bump it up to 400hp . If anyone has ideas that'd be great. I'm kinda wanting to keep it a automatic tras as well.

 

Hey, good luck with the car. These Darts and Dusters are pretty simple cars to work on. Parts are usually cheaper than those for the Charger/Road Runner cars or the Challenger/Cuda.
The 360 engine is a great fit for the Dart. Getting to 400 HP will require a pretty radical camshaft compared to what was stock. The MP 360/380 crate engine used a split pattern cam with .513 lift. I hope that you don't mind a rough idle, because as you step up in power, the engine will become less streetable.
400 horsepower sounds cool when you are bragging to your buddies. The stock 1968-71 340 4 barrel was rated at 275 HP and it was a solid 14 second performer. It idled smooth and got decent mileage. If you decide to step it up by 125 HP, mileage will certainly suffer and driveability will decrease. This isn't meant to turn you away, just an effort to inform you that going fast means a few compromises will occur. Running a 400 Hp 360 means you will need a durable transmission with a high stall torque converter. The 727 is the obvious choice here. A factory converter will not be enough though because most were rated at or below a 2500 stall rating. A 400 HP 360 engine makes its power up in the higher RPM range. Because of this, a stock type torque converter that gets the car moving from a 600 rpm idle will not work. You will need at least a 3000 stall converter. These can be found from many sources and are usually 9 3/4" to 10" in diameter.
The rear axle is the easy part. The 8 1/4" axle would be durable enough if you stayed under 350 HP. These axles , like any other, will be stressed MORE if you are able to actually get traction. If you stab the throttle and the tires go up in smoke, the drivetrain isn't stressed nearly as much as when the car actually hooks up and scoots. If you are serious about that 400 HP number and you want to hook it up for low dragstrip times, only an 8 3/4" axle will do. You'd also need at least a 3.55 or 3.91 gear with SureGrip to make the most of it. These axles are out there but you will pay through the shorts to get one. A complete A body 8 3/4" axle with a 3.55 gear will likely cost a minimum of $800 if you can find one. Some people choose to find a 66-70 B body axle and then move the leaf spring pads in 1/2" per side. This B body axle is much cheaper since they are much more common. One can often be bought for $200 or less. The axle wis wider though, and using it in the Dart sedan body requires a custom wheel offset. I had a 68 Coronet 8 3/4" in a 67 Dart. I used a 15x8 wheel with a 6" backspacing. If you haven't already picked the wheels for the car, this isn't a big deal.

 

Hey thank you very much for the information! you've been really helpful, yeah 400 was just a number I was somewhat thinking about but if its going to be a pain then i have no problem stepping it down. this little tinker toy of a car doesn't need very much to make it a blast to drive anyways.