<VV> Differential tale of woe.

[Jeffrey Hennessey]

I was driving my 1963 Spyder Coupe, with my newly rebuilt engine, when I was shifting from first to second there was a bang, and suddenly I was coasting. I got the rear wheels off the ground and they are no longer connected to each other. 
Tomorrow I begin my search for a replacement differential. Can they be changed without removing my newly rebuilt (costly) engine?
Any other guidance that anyone can offer will be greatly appreciated. 
Thank you, 
Jeff
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