8 3/4 identification

[Rengo]

Does this check out on the casting number?
2070741
270 gear ratio
back of plate to back of plate is 53"

I need to know if this is an 8 3/4 that can be put into a Duster for racing.
I don't know if it is clutch or cone because it has never been opened.

 

[Rengo]

Can someone also provide information about how to identify clutch or cone.
Springs = cone?

 

[5.7 hemi]

That more than likely has a 2.76 ratio, 741 case, and the clutch sure grip case has left handed bolts on the pass. side brg. and there are NO springs in the case.

 

[Rengo]

If the years are posted 1965-1972 I can still work this into an A body right?
With these gears do you think it would be worth picking up?

 

[fishy68]

Their highway gears, not performance gears. If it's a sure grip and in good shape it may be worth picking up. 53" backing plate to plate is close to an A-body rear but the backing plate to backing plate is not the best way to measure a rearend because the backing plates are not flat and hard to find a spot where the tape measure sits good. I can't for the life of me figure out why some guys do that. What matters is where the wheels set in the wheel wells so that means the best measurement to go by is the drum to drum measurement which on an A-body is 56-5/8". Yes a cone type has springs that you'll see through 2 windows. A clutch type has no springs and multiple windows all around it.