Okay, Ive been here and done this- way back in the early 1990's when I did not know enough.
I had a friend pass away early, leaving a wife and two kids- cancer got him before he turned 30- we had worked together falling trees, he stuck with it, I did not.
When he passed he had an old beat up 066 in his garage- worn beyond practical use- but a potential parts donor for main work saws.
I got hold of it, decided to do it up in honour and memory. Did what I thought was enough- new main bearings, new piston new cylinder and a few other things- same old crank that had done a million hours as a forestry saw.
Got it all together and it lasted about 2 hours before the bottom rod big end bearing let go and took out the top end.
Shelve that 630 and cut your losses.
162SE if you can find a good one is your parts donor for it. You might find a reasonable 162 with a busted magnesium tank or something- all you want is the engine- not the bolt on bits.
In the meanwhile, try to find a Husqvarna 61, 266 or 268. They can usually be found in reasonable condition and are pretty much the same chassis family as your 630- but easier to find parts for- genuine and aftermarket.
That will get you a dependable saw- then you can worry about the Jonsered as opportunities present themselves to do something with it.