I think you are closer to 11:1 cr with your combo
(723 + 5 + 4 + 9 + 55) / (5 + 4 + 9 + 55) = 796/73 = 10.9
When figuring cr on a sbc the piston is typically below deck 0.020" or 4cc and the head gasket is about 9cc. Hard to machine 4 cc's out of a head, I'm thinking maybe 3cc off from resurfacing. You really need to measure that to be sure. 1 cc of water weighs 1 gm
Get a 0.060" or 0.080" thick soft copper head gasket set.
A 0.060" head gasket will add around 4.5 to 5cc more head volume over the standard 0.040" head gasket. A 0.080 will add 9 to 10cc.
Place the head gasket on the head and scribe a line around the gasket. Then unshroud the valves all the way to the head gasket. Should add about 2cc more to the chamber and improve head flow.
A 11.0:1 cr 350 will drop to 10.1:1 with 7 more cc's and 9.6:1 with 12 more cc's.