How extensive are the changes you made to the new template? If they are relatively minor then you can just recreate them in the other part. There really is no easy way to grandfather the updated template backwards.
Another thought that comes to mind is you can start a new part using the new template, then insert the other part in as a derived part. Problem is if you need to modify the old part, you need to always go back to the original part to do so.
If this solved your issue pleasemark this posting "Accept as Solution".
Or if you like something that was said and it was helpful, Kudosare appreciated. Thanks!!!!
Best Regards, Scott McFadden Inventor Professional 2014 (Colossians 3:23-25)