The 67 needs some differential work...

[67Chvl67]

This car is new to me. I've been noticing noise and vibration lately, after getting the rear on jacks found my problem. The bearing at the yoke is toast, tons of play. Since I'll be spending money on the bearing repair figure its a good time to change gear in the rear end. I have 3.90 gearing currently. My main question is, if i want to switch to 3.42 (new crate 427 engine), am i replacing the pinion ring and, the differential? The diff i have should take anything between 3.08 and 4 at least right? So just swap out the gear right? Also, never had this rear end apart but its a 12 bolt. Should i assume 30 spline?

I'm diggin this site, thanks!!!