I have vastly speeded changing the starter by using a 1/4" drive extension of 24" length.  I run it under the headers and it fits nicely right onto the upper mounting bolt.  I can change the starter in ~15 minutes.  I still have to jack up the car a little to get my body under the car.

As to the starter - try to get a new one rather than rebuilt.  I have had rather poor luck with remanufactured ones.  Also take your starter in and verify that its nose is the same as the new one.  Different companies have switched the part numbers on manual vs auto trans.

5 bolt blocks came on 64 1/2 and early 65's.  It's been a while, but you might be able to tell by looking behind the block at the top of the bell housing.  A 6 bolt will have two bolts at the top vs one.