Im looking at buying some spare parts for my XR's but dont know how to I.D. vs. a standard Bravo I & the parts inside. Any quick tips or things to look for on the outside?? Thanks

Prop shaft would be the first thing, though an XZ also has the larger shaft.

Pull the top cap and look at the gears. Bravo 1, X, XZ all have helical cut gears.

Input shaft bearing retainer is totally diff than std bravo
So if that's diff next step is pull top cap and ck for straight
Cut gears

XZ and XR are the exact same lower.

So if my current setup has the smaller output / prop shaft its most likely a std. Bravo I or can u put a std. small shaft lower on a XR upper???? I have not pulled the drive to identify the input shaft retainer or measure the knuckle as those are larger also.

Yes. They can be swapped.

A lot of things can be mixed and matched, the only good way to know if it has XR gears is to pull the top cap and look for the straight cut gears. As has been said, the XZ is and XR drive with helical cut gears in the upper. So everything is the same on the outside, just the upper gears can be different. And you can swap between XR and XZ upper gears without fitment problems.
Hope that helps.
Dick

Yes, thanks for all the tips! i thought there was a bigger difference maybe an easy way to ID one from the other. Thanks again for all your help!

X and XZ's crunch when you turn them, XR's have gears sticking out the side!