GM 14 Bolt wrecked-how to tell?

First, you can count the splines, and ring/pinion gears should be stamped, or you will have to calculate the ratio. (number of ring teeth over number of pinion teeth)

The spider gears and yoke, should be standard for a 14 bolt unless hi-proed.

These may be separated by production runs, indicated by serial numbers, as you don't indicate the original application for this RE.

(6.50 or above would be a very low gear. 4.11 or 4.60 being typical.)

The 10.5 is a full floating axle. The 9.5 is a semi floating axle. A 1500 truck would usually only have a 9.5 in it if it was a diesel and never would have had a 10.5. Many 2500's had the 9.5's, especially the lower GVW versions. You usually had to have a 2500HD to maybe get the 10.5. A 3500 had the 10.5. A 3500 HD may have had something bigger.

The full floater has the big hubs that stick through the center of the wheels. These hubs have I think 6 bolts in them, when you remove these bolts the axles will slide out leaving the wheels still supported on their own bearings. The full floating axles only come in the 8 (or more) wheel lug versions.

The semi floating axle does not have the hubs that extend out the wheels. The hub is basically flat. To remove the axle you have to first remove the wheels and all the brake stuff then take the rear cover off the diff and remove a pin out of the carrier so you can then slide the axles further in and remove the C clips that are in a recess in the spider gears. Once the clips are removed the axle and hub can be slid out of the housing and the bearings stays in the axle housing. The semi floating axles come in 5,6, or 8 lug versions.