You have a 3.42Z ST-10, with or without the 904 steel case this trans is rated at 285 ft/tq...
What makes these weak is the input gear has 17 teeth and the mating gear on the cluster has 31 teeth... M-21 has 26T input/27T cluster...
I buy these all the time with blown input and cluster gear to get the good main case...
Your final drive in first gear with the 4.10's would be 14.022, good for 20ft before you have to shift...
The early Muncie's are 21 1/4" long, the ST-10"s are 22" long, so you might need a drive shaft shortened...
You might want to rethink what your going to do...
E-mail me if you want to talk about it... Crash
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