From my first reply, I know that engine bearings are basically unobtainium. Once you pull a motor apart and start into plasticgauge, the assumption is that you can get bearings. Not so (at least for now) with 4-cylinder wings. I would lean towards using the bottom end of your donor engine as-is. Unless you have already confirmed that it needs a full rebuild. Then I might start looking for another donor. That's me, YMMV. I had a '76 with a kicker, and now have a '78 w/o. I would prefer to have it (for emergency use), but on the 'Wing they ain't very user friendly, and I don't think I would tear down a motor just to have a kickstarter. I would simply swap the top end/valve train, and mark the flywheel. Robin and Cyborg are far more experienced than I, and unless I mis-read their replies, I think they agree. In any case, good luck with your project!
Current: 1978 GL1000 - JUNE 2017 BOTM
2006 Kawasaki Concours: Sold
1995 Kawasaki Concours: Crashed/totalled.
1976 GL1000: LAST RESTORATION, sold
1981 Honda CB900F Supersport: 3rd restoration, sold.
1979 Yamaha XS-750F: 2nd restoration, sold.
1982 Honda FT-500 Ascot: First (only) new bike. Family forces sale.
1973 CB500 Four: First restoration, long gone.
1972 Suzuki TS-100: First bike, sold.
Only dead fish go with the flow . . .