I replaced the seals today without much trouble and so far the pump doesn't seem to be leaking, at least not as much as before. It's hard to tell since it has been raining today. I'll be able to tell better once the concrete pad it sits on dries out.

I'm not sure if this is because these seals are aftermarket parts, but the housing gasket and the strainer basket gasket were a little too large. I did manage to seat them properly after fussing with them a bit. The other seals seem to fit perfectly.

Thanks Waterbear, I greatly appreciate your help.