How would you rebuild this 318?

Sounds like a good plan. IDK if the OD trans is a good route to travel. The first gear is a blast. You’ll have to rev it up a little more for that RPM drop into second. Third is a normal shift and OD is for the Hwy.

If you really want it, then do it. It should change the 3.73’s to a 2.60 - ish rear gear feel. The car won’t like much of a camshaft duration increase.