Axle Splines a Little Rough??

They don't look right but it's not real easy to tell everything by pics on the net. Since you bought it off of E-bay it's entirely possible the SG was a mix and match of parts from several units. A lot of guys do that, save up all the old broken sure-grips and use whatever parts fit to make one that works. That's not always bad as long as you match things up correctly and use real good parts but you get some guys that throw questionable parts in just to make it a saleable piece. If you have a driveline shop near you drop by and show it to them and see what they say. Someone with experience looking at it in person should know right away if it's a problem. Take the axles too so they can see what happened to them.

BTW: have you set up gears before? Got all the tools to do it?