Rear End Confusion

[ytcharger]

I have a '69 charger 440 r/t. Want to rear end from 3.55 to 4.10. I just put the Edelbrock Performance RPM kit on it so the low end is somewhat compromised. Other than that, I have no idea what casting number is on my car? I can't see anything the differential since it is coated with dirt. Summit Racing guy asked me what casting number and I have no clues. I do know it is a stock differential - posi 3.55 that's all.
How do I find out if it is a 479, 488 or 489?? Any help is great...Thanks ahead.

[A383Wing]

get a wire brush and start scraping the dirt & road crap off the case.....you will find the numbers he needs. I assume you have a 8-3/4 rear? You will just need to scrape the pumpkin, not the entire rear diff assembly

Bryan

[ytcharger]

Yes, it is 8-3/4. I did start scraping and probably scraping in wrong places. Thanks for tip. Will go back and scrape some more.

[c00nhunterjoe]

Left side, where the shaft mounts. Will be 742, 741, or 489 digits at he end of a long string

[A383Wing]

 

[ytcharger]

that pic helps a lot...I can see the last 3 digits as 489. Thanks.

[c00nhunterjoe]

No problem.