Those bearings come split.
Ie,thatīs the way theyīre supposed to look.
Only reason i can see for the block side bearing to go awol is that it must have seized out of some reason,and the main Q would be what caused it.

Install of new ones-both the block one and the timing cover one-is as straight forward as it gets.
Like stated above use a hacksaw blade and just knock them out carefuly.
Install with a drift and a hammer,no aftercorrections should be necessary.
To clean the recess out use a pair of tweezers and after that liberal amounts of petroleum based degreaser and a brush.Let rinse run to the ground(Ie;do this before you put the pan back on)

I guess the scoring on the front bearing is from the rear breaking lose and the shaft then wobbling around?
Check the bearing surfaces of the dist gear with a nail.Pull it across the bearing surfaces and NO resistance should be felt-at all.
If it does,take the shaft to a lathe to have it micropolished with extremely fine emery cloth.(800 up and water)

One reason for seizure could be lack of lubrication.
Either from the oiling hole not having been completely true with the delivery hole or from to tight a clearance(altho thatīs less likely)
IOW,try and investigate the cause.

That these engines "eat" gears is normal.One of the sidekicks of running to soft a chain if you ask me,and worn gears are more or less to be considered OEM over time.
If they get to be completely out of whack(yours obviously isnīt) all isnīt lost.
The lower ones are stock 102 ones,and as such aint an arm and a leg.
The cam ones tho...are highway robbery.
..and the beuty is that these can be modded with industrial parts without to much hazzle,however..again a lathe is needed.
None the less it IS worth the effort seing what merc as well as aftermarket vendors charge for them,and the gears are an industry standard 3/8" split.
Thatīs a job for a machine shop tho-like mine.
Check the pricing..and get ready for the laugh of a lifetime...cause merc REALLY went up the wall on that one.
The duplex chain boys are even worse off than us simplex 2.3 guys.