I bought a TH350 with a cut output shaft.. need to put in a new one during the rebuild..

The question is..

Is it better to go with the shorter output shaft.. or shorter drive shaft?

My thoughts are the shorter the drive shaft the better..

It’s in a 67 C10 longbed with a mild 292.. so the driveline is already ‘yuge..

Cheers!

If the D/S is short, taking anything off increases the range of pinion incline angle during suspension travel and stresses the U-joints.
With your long D/S I think you're safe to take some off.

The shorter tailshaft and housing is MUCH stronger!! We often substituted the shorter TH350 in anything even remotely high performance when I worked for the big transmission shop in Nashville.

We did most of the hotrod and racing builds around here back then. The rear drum and planetary holds up much better in the short version, so we would have the local drive shaft builder install a new tube in the driveshaft for the customer.

I defer to someone with actual experience, makes sense to me.

A special note here.

GM built a turbo 400 with an extended output shaft that was splined to the smaller 350/700/200/PowerGlide size. Nobody liked that long tailshaft and housing, but it would substitute directly for the long shaft 350 and was considerably stronger. The rebuild industry called it a 375. I'm not sure WHAT GM called it.