differential swap

The ratio will be stamped on the crown wheel or on a tag on the differential. check that it is the same.

Everything bolted right up but the spindle for the drive shaft would not. so can I use the spindle off the old differential?

What are you referring to as a spindle?
Do you mean the flange on the front of the differential that the rear end of the driveshaft bolts to? #2 shown here?
Does that #1 coupler unbolt from the end of the driveshaft?

Yes, the flange on the differential.

Does the coupler unbolt?

Yes.

Okay, does the coupler from the other driveshaft fit on this one? If you do not have it you may want to check if it will fit on this driveshaft because you know it will fit to the differential flange.

I have it but it does not fit the drive shaft.

You may want to check near you for a driveshaft shop that can help you fix this problem. perhaps they could cut off and weld the end of the driveshaft that this coupler does fit the flange onto the driveshaft that fits this vehicle. Did you by chance just check if the entire driveshaft from the 2010 would fit? Or if it is a two piece if just the back half would fit?