When I set up for cruise in my 59 C-182 at 11,500 I set at WOT which should give you between 19 and 20 MP and then adjust to 2150 RPM. Lean as required and manage your CHT to 380 or less. I suspect you should see about 10.5 GPH at those power settings and maybe a TAS of between 118 - 123 Knots.
BTW- When I watched your airplane on ebay I could not believe the price. I really wanted to buy it myself but could not come up w/ any justifiable reason to own two 1959 C-182's
I suspect you got that plane for about $40k. Best deal I have seen in a long time.