While investigating odd knocking noises from the engine (turned out to be a noisy tensioner pulley), local mechanic Graham from RD Motors removed the old crank shaft oil seal and found marks on the shaft where it spins inside the seal (just after 1 o'clock in the pic), and silicon when once a chunk of aluminium had been (just before 3 o'clock in pic).

It looks like someone has taken a swing with a hammer and screwdriver in the past - presumably trying to remove a stubborn oil seal

I'm wondering what the best course of action is to repair the damage. I think

If so, what's involved in removing the oil pump? I guess an engineer could repair the oil seal bore (aluminium solder and some machining?). Or maybe a replacement oil pump would do the job? I can't find much on the forum - or anywhere - about changing oil pumps, so not sure if this is a can of worms.
Any thought or ideas gratefully received!