Found a slightly better way...
I changed the last 2 levels from fighter2 to barb and sorc.
Dwarf with 20 con, start lawful good align, switch to neutral good at 3rd level
Levels (max/avg HP at each level)
Level 1 paladin, feat toughness, 13/13 HP
level 2 monk 8/4.5
level 3 cleric, dwarf's toughness +6 HP, 14/10.5
level 4 barbarian 12/6.5
level 5 fighter, giant's toughness +9, 19/14.5
Level 6 fighter, dragon's toughness +12 taken twice, 34/29.5
7-18 fighter with dragon's toughness taken every other level as bonus feat
7 10/5.5
8 22/17.5
9 10/5.5 + 12 dragon toughness feat
10 22/17.5
11 10/5.5
12 22/17.5 + 12 DT
13 10/5.5
14 22/17.5
15 10/5.5 + 12 DT
16 22/17.5
17 10/5.5
18 22/17.5 +12 DT
19 barb 12/6.5
20 sorc 4/2.5 get toad familiar
Maximum HP = 346, avg = 273.5 (let's round up to 274).
Now let's add in con. 20 at first level + 5 stat increases + 5 inherent (tome) + 6 amulet of health + 4 raging + 2 toad = 42 con. A 42 con gives a con bonus of +16. 16 X 20 levels = 320 HP.
Max HP = 666, avg HP = 594.
666...my favorite number.

This combo has 4 more maximum HP and 6 more average HP than my previous attempt.
Maybe this should be added to the smackdown thread.
