My thought is to remove the alignment taper and install it inside the engine at the second bearing. Then install the bar through the tapper then back to the last bearing. You would still be able to hit the bar but holding the taper tight against the block will be a hand full. If this were mine I would install the inner
bearings first. Check to see if the cam fits after EACH BEARING has been installed. If it is in at a cocked angle the cam will not turn and you will need to adjust it if possible. After the easy ones have been hammered in take the driver end off the bar and using a brass hammer and the driver end install the end bearings. Install the front one first and then try the cam again. Then install the last bearing in the same manner. AGAIN CHECK FOR FIT AFTER EACH BEARING HAS BEEN INSTALLED.
There are other things to watch for but this is how I would use this tool.