El Tigre 500 free air crankshaft fitment????

Hey guys will a 1979 el Tigre 5000 500cc crankshaft fit a 1981 case? I know there was a new part number assigned to the 5000 sometime from 78 to 81 but wasn't sure I found one for cheap on eBay

El Tigre 500 free air crankshaft fitment????