Imagine no timing light, nor timing marks or tape or even a zero marker. NOW, what I would do from there is take off the valve covers and watch for number one compression, IE no rocker or spring movement, this is given the motor was put together correctly. TO be closer than just guessing on the lobe of the cam, I would set the (hopefully the damper has some sort of mark, even one put in by a tapered punch) at about 1 o clock, drop the distributor in with the number one at about where you assumed it, pointing towards the center of driver valve cover with the stock vacuum advance pointing at the passenger center valve cover. This is just to because the vacuum advance doesnt like the other side for aesthetics, etc. Now all you gotta worry about is that when you put the cap on you do it right. Thats if you dont have much to go off of I think, if you got marks, tape, lights it just gets easier, but I always get it started before I put a light on it, and the spark method works good too, just keep your thumb away from the spark...it gives a nice 50 000 volt or so shock...WEEEE!
And...what? no stock marks, tape or idea of what degree to time to?? If you're good go by ear, startup, hot startup and seat of the pants...thats the MOST accurate method ever devised for sure, no doubt about it. Do it any way you want, the small block chevy is pretty easy to time and set the valves on...or any engine if you go with the running mate method. K I think I've said far enough thats been said before...oh did I mention the 4 beer I downed while writing this??