67 12-bolt to SM 465 Transmission

[Rich1972C20]

Guys,

I'm looking for a cost effective/easy solution to mate my SM465 to 12-bolt axle.

I swapped in a 350cuin/sm465 in my '67 C-10 which had a 6 cylinder SM418. Obviously the driveshafts don't match. The 350/SM465 came out of 72 C-20 with Dana 60 axle. The 72 driveshaft has a much larger diameter and different mounting arrangement than the 67 (see photos). As I see it the options I have are as follows:

1) Custom driveshaft. My concern here is can the 12-bolt handle the added torque (about 400ft/lbs)?

2) Swap out the axle with one that is compatible with the Dana 60/SM465 configuration (did chevy make this?). I would use the axle from the '72 but it is a leaf spring suspension (my 67 is trailing arms) and it has 8 lug bolt axles. Also not sure if the axle length is compatible with my '67 configuration.

3) Put in a different 4/5 speed transmission that I can use with my current axle.

Bonus question, if I can use my current 12-bolt axle can I make it a posi? I believe that there is a difference between a passenger car 12-bolt vs a truck.