Hi, it's many years since being in there on a 360a model but just looking at the cmsl parts pic it apears that it just pulls out once the pump is off.
The collar/bush/--looks like they call it a metal-worm shaft out--um, ok that--i would just carefully tap it out once the seal is out of the way then swap it into the new case.
Maybe warm the case around that area but i doubt its in very tight.
I was around when those bikes arrived in "74 but probably never exactly done what you're doing now.
Although i did remove all the pump & parts on my new MX250 in about "73-"74 but too long ago.
Regarding lining up the drive, just eyeball it.
I'd either pick vertical or horizontal on crank & shaft rather than odd angles, it'll slide on easy. You'll be right.
I'm reading this as a private message but i see the question on the site, so i'll post my answer there too just incase i need to be corrected by others on anything i said.
Are you in OZ? just thought i saw BigPond on the email. Cheers from NZ further down under.

Yes, from down under, in Canberra

Do you know, does the collar fit into the cover as well as the oil seal?
Or does the collar fit into the cover and the oil seal just slips over the metal worm shaft?
I don’t suppose anyone has a photo of the oil seal and the collar fitted?

The collar will tap in carefully from the oil pump side & the seal will fit from the inside up to a limiting step pretty much where the collar ends up flush with.
But now i'll see if there's any pics out there although i cant see it being any other way but happy to be corrected.
Gotta be careful not to damage the collar or the shaft might get grumpy trying to revolve or fit through. Cheers.
ps, maybe i'm misunderstanding your question but can you not see on the old cover how it all goes.
I'd just flick the old seal out with a screwdriver so as to get at the collar then drive the collar out with a brass ened punch.
Think i have a collar on an old pump of my earlier model so i'll go see for a pic.

Here's a cover with multiple pic to view. But i have no luck linking ebay so if it doesnt work just put in 1511855550
www.ebay.com/p/1511855550
Ok, it seems to work this time or does this end.
Can't find my collar to view, found the pump but thats no help.
It's made out of something like cast iron or cast steel or something by memory, but not brass & will have a slight step down for a short distance where it presses or taps in to the case.

Thanks, that picture helps.
I haven’t taken the old cover off yet. I want to know as much as possible before removing it.
I don’t want to take it off then find I need more bits or that I can’t finish the job.
Do you know if any part of the collar actually goes into the oil pump itself?

Yes it goes well into pump body. Just google & you might easily find one to view to get a good idea.