The slotted adjuster bar isn't normally a problem. That also has a rubber mount at the engine end. If you just need a thin washer that's fine. If it will flatten with a hammer that's fine too. There are some with a distinct dog leg in them which I think are actually for alternators but could mount to the other side of the top generator mount. The usual problem is the elongation of the two lower holes. Being alloy means they wear easily. The cause is not doing the bottom bolts up tight enough after doing the belt adjustment. Using a lever to set the adjustment will tend to push the dynamo out of line and you need to nip up the adjuster nut before diving underneath to get at the lower bolts. These are a pain as there is little room to hold two spanners and turn one end at the same time. OK if you have a lift but not when grovelling on the ground. Means that "it'll do" comes into play before they are really tight. If the holes in the plate are badly worn it's usually the front one that is worse so the dynamo then takes a twist. The belt can cope with a small amount of misalignment but comes the time when, although it is working fine, it triggers your OCD!
I guess that it would be possible to drill out and rebush the end plates if the hole isn't badly damaged. Has anyone done that?
Bottom line, just convert to an alternator!