14-bolt Parts Compatibility

[bigtexasrob]

All right, long story short, I threw away the axle I needed, kept the axle with the diff I needed, and bought an axle I thought I needed.

Truck in question is a ‘74 C30 Dually. The axle under it currently is a SRW 14 bolt with an open 3.42 out of a ‘93 C2500. The axle I just picked up (without doing any measuring like an idiot) is a dually, open 4.09 that appears to be from a cab and chassis (meaning it’s the stubby 63.5” WMSW instead of the 72” dually.)

My question is this: how much of these two axles can I hodgepodge together and how close will it get me to the 72” dually with 3.42 final drive?