I hear you panic but with all of the rockers and push rods removed all of the valves will be closed and no cam movement is necessary. It wont matter whether the motor is on the compression stroke or not, just as long as the piston is coming up in that cylinder. All you are trying to do is sort out whether the cylinder is holding compression. A good number of years ago when I was in my late teens or very early 20s, I had a new timing gear set that was mismarked that I had installed in a brand new 235 I had just rebuilt. Fired the brand new 235 up only to have it sputter and not start. An older mechanic come over to look at it and watched the valve movement and thought it was out of sequence. Did a compression test and all the cylinders came out low, really low. He pulled the rockers and push rods and did the test over again and still low. That is how he figured out the intake valves had kissed the pistons and that something was amuck with the cam timing, either bad cam or timing gears. That being said, a leak down tester would be the better approach if you have one, I don't, so I go the old school backyard hackerwork route. Just my experience with these motors.
