Was trying to figure out how to do this at home because of the PITA getting a block to the machine shop by myself. Anyway, after trying to use a home made bolt draw-in style installer for the rear #5 bearing that didnt work, I had an ah-HA moment. Why not use a old camshaft to press the rear bearing in? Slip the bearing over the cam, thread in the cam so the other bearings are supporting it and use the gear on the SB cam as the drive. Tap it in with a 3 lb mallet. Worked perfect! All you need to remember is that the hole in the bearing MUST match the hole in the block. Put a bolt in the cam or hit with a brass mallet to prevent damage to the snout of the cam, but I had an old junker to use. Same principle with the correct tool (which I can actually borrow for the other 4 bearings from a mechanic I know). So if you ever have to replace the #5 bearing on a Sunday night here's how ! 
I think you can do the same with the front by using the timing chain cog. Put bearing on cam, install cog and thread cam into block. The cam will keep the bearing straight and the cog will push the bearing flush into the block by driving the cam in by mallet. Slip the old bearing on the same cam and start all over to countersink the new bearing. The trick is to use the cam bearing race as the guide to keep the bearing square. If the hole doesn't line up, you can use a long drill bit through the #1 main to redrill the oil hole, Ghetto Garage 101!
I think you can do the same with the front by using the timing chain cog. Put bearing on cam, install cog and thread cam into block. The cam will keep the bearing straight and the cog will push the bearing flush into the block by driving the cam in by mallet. Slip the old bearing on the same cam and start all over to countersink the new bearing. The trick is to use the cam bearing race as the guide to keep the bearing square. If the hole doesn't line up, you can use a long drill bit through the #1 main to redrill the oil hole, Ghetto Garage 101!