I am at a tipping point with my car. I have spent quite a bit of time undoing the sins of it’s past. It has a new zz454 crate motor, and a rebuilt Muncie M20 4 speed. Working front to back, the next step is the rear end. It has a 10 bolt 355 with an open diff....horrible. I am ready to swap the rear end. The horsepower and the torque are good...I just don’t feel like I am getting the power to the ground. I am thinking about a Mosier 9” 373. I am just looking for some advice as to the best way to make the car faster. Would my motor/trans/rear end setup above make a significant difference? From what I have read, the combination working together means everything. I am not prepared to do something different with the tranny, but I feel like it’s workable. The suspension is basically stock. Any input would be much appreciated. Understand I am a bit of a newbie when it comes to A lot of this.

 

Personally I like 3:90's better but 3:73's would be a little more highway friendly,that decision should be based on where you do most of your driving city or highway.
If you haven't already done it subframe connectors should be installed,hooking up all that power to the pavement can twist the body and you don't want that.
The M20 will do just fine but I'd highly recommend a scatter shield,stock bellhousings can break under a heavy torque load (been there done that with a 427/4speed) and a clutch explosion can go right through your floorpan and that's not a pretty sight when you are sitting on it.
Multileaf springs and traction bars of some kind should be part of the package as well if you don't have them.

 

Thank you for the info! I run it a little on the highway...I live out in the country so I am about 20 miles from anywhere. I will check in to the frame connectors and the scatter shield. I do have Multileafs (a whole other thing...they are 2” over stock to accommodate the tires), and I have looked at some pretty interesting traction bar set ups. Sure appreciate it!

 

Glad to help,keep us updated on that fine ride.