I'm breaking with my habit of not responding to 67th Tigers, because this is not something covered often enough to be familiar to the average reader (unless I am mistaken):
http://ehistory.osu.edu/osu/sources/recordview.cfm?content=/005/0007
For the main army of operations I urge the following composition:
.
250 regiments of infantry, say ........... 225,000 men
100 field batteries, 600 guns ............ 15,000 men
28 regiments of cavalry ................. 25,500 men
5 regiments engineer troops ............ 7,500 men
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Total .................................... 273,000 men
This is not remotely realistic or close to what was done OTL - but of course, for those who thought they never had enough of anything and couldn't move an inch until they got everything, its surprisingly small. I mean, its only over twice as big as the Army of the Potomac at its height.
The suggestions begin on page 5 and end on page 11.
Note how McClellan assumes Johnston has two or three times as many men as he actually did, and that they are far better equipped than they actually were.
Whatever Mac was on, I'm glad Grant wasn't on it. The US managing to lose the war in 1864 because of such calculations would be criminal.