Went digging in the junkyard today with the CV spider in my pocket.
Turns out the 02 explorer has the same diameter shaft ends... but courser splines.
The good news is its a solid heat treated shaft and its the same thickness its whole length, necking down only for the splines.
I also called moser and talked to them about sending in a core shaft and paying for two pairs of CV axle spline service and they're happy to do it so long as they look everything over and it seams like it works.
Cutting the heat treating off the hollow shafts just wasn't sitting well with me.
I also discovered that the two left shafts are different on the ends in diameter and one had a slightly smaller cv joint pair...
I'm guessing i got one v8 shaft and the other from a v6 car. Both are splined the same into the housing and at the hubs... but one is stronger than the other with bigger cv joints.
The left and right v8 shaft have the same size cv joints... its just the spare left shaft had some differences.
Going back to the junkyard tomorrow to compare my cv joint to the explorer outer cv. If they are the same internally i plan on building a hybrid cv. But if they're different I'll pay for 2 pairs of spline service and know that I'll never have to worry about the strength of those shafts...