I was watching (briefly) one of the biker build off shows recently and actually got a good tip from it. They were installing an engine in the frame, they lay the engine down and lowered the frame onto it. That may not be possible for you if the wheels and forks etc are on it, but...if you can position the engine in such a way as to lean the bike onto it, it could be cool. A combination of solid hard things and soft flexible things to lay the engine on at the appropriate height and angle...even if all you do is get it in the frame so that you can then pick it up straight and then jack the engine around to get the through bolts in.
But Evil's right, it's a lot easier with an extra pair of hands.
with the cb350 the frame is assymetrical, so it can only go in from the right side. the lower of the cradle side. it can be a litte bit of a puzzle to get it in and out, but once you do it 2 or 3 times, youll have it perfectly figured out and will be able to do it alone. it helps to stand up over it and lift it into place and out of the frame. at least for me it does. you can shove a blanket into the area to help keep from scratching it.
Don't tighten any of the engine mount bolts until you've got them all in place. You may need a floor jack beneath the motor to help. I agree on removing the left hand exhaust studs. Pulling the starter (and blocking it off 'cause electric starting is for wussies) really helps too.