I think you can even do this with the engine in the bike. Remove enough of the head bolts to let you lift the rocker box. Loosen the cam chain adjuster. Need to remove the points and advancer covers and all that stuff to. The housings need to come off.
With a little help to hold the rocker box up you can lift the end of the cam enough to slide the cam bearings off the cam. Two on each side. After you slide the new bearings on, do the other side. After you get the bearings on push them as far on the cam as you can, then center them in the head. I use the depth gauge part of my dial caliper to measure each side.
As I said I think it can be done with the engine in the frame. I haven't tried it myself.
Good luck I hope it works out ok for you.