Mk1 rear bearings fail far to often. And they also seize up and spin in the hub making any new bearing flop around so make sure you look out for this..... just threw some drums away so i knew people would be needing them the next day but hopefully you dont. I still have some spares. Discs easy to get the drums not so easy.
Put a glove on and put the wheel grease on your hand and wipe the bearing back and forth on your hand to force the grease into the bearing properly. make sure you have the iside packed with enough grease but not so much that it will come through onto the shoes.
Dont fill the cap with greae but do put some silicon on it or at least some grease around it to seal it properly i have seen many rear bearings rust out from water leaking in.