The outer bearing should be a 6208 (NOT 6308). It is 40 x 80 x 18mm.
The 5208 is 40 x 80 x 30.2mm. The SKF website says that the 5208 p/n has changed to 3208A-2RS1. A Google search seems to indicate that the 5208 p/n is still available.
Since the double row bearing is 12.2mm (0.480") wider, you will need to shorten the bearing spacer by that amount.
John