Brian,
I would pull the plugs, get a helper to operate the starter, and with the gauge stuffed in a hole (or screwed in) have the helper give it a stomp for about 6 revolutions or so and check your gauge. It sounds like there is no wiring yet, so just stomp away.
Remember you are looking for both adequate compression and little variation between cylinders. I would want at LEAST 95-100 psi for my high reading and a variation of not MORE than 10 lbs. These values would indicate a engine that would work, but wasn't new. Any large difference on any one cylinder would indicate a problem with that cylinder...enough rant, good luck. I just re-read...no cab! Push on little button on starter switch.
Stuart
