The service manual lists a 350 2 BBL at 9.2:1 and a 350 Qjet as 10.5:1 CR. The rpm factor is as the piston compresses the gases in the cylinder some leaks out past the rings and maybe past the valves, if the engine was only turned over at one rpm some would escape faster than the piston could compress them, hence the test rpm of 155-165. What ever your starter will turn the engine over with all the plugs out will be fine. I wouldn't worry a great deal if the readings are a bit on the low side as long as all eight are close to the same reading. If one or two are a good deal lower you may have a problem in those cylinders.