I have a 68 Dart with 7 1/4. I bought a 8 1/4 with 3.21 from a 75 Dart. I have a set of small bolt pattern 8 3/4 axles also.

Will the 8 3/4 axles interchange into the 8 1/4 housing? Neither are sure grip.

Thank you all !

no, nothing will intrchange,-the axles,brake drum assemblies look similar,but it won,t work.just put the entire 8 1/4 rear in, and convert the front to 73-76 disk brakes,

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V8?? We don't need no stink'n V8!!

The axle shafts do not interchange. 8 1/4 is C-clip with straight roller bearings in the axle housing and has 27 splines. The 8 3/4 axle is retained by the tapered roller bearing which is pressed onto the axle and has 30 splines.

Swap in the whole axle assembly and the shorter driveshaft from the later Dart. Upgrade you front brakes when you can afford to do so.

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Joshua