Are you rebuilding a motor, or are you repairing a motor that jumped time on you?
If you are repairing, keep in mind that it is very likely that the distributor may be out of sync with the normal timing. This happened to me with a Cadillac 472 motor that jumped time on me. (stinking teflon coated gears...)
Anyway, go ahead and find out where TDC is on your #1 cylinder. I used a small wooden dowel through the spark plug bore to do this. It may be handy to have an extra pair of hands and eyes helping you as one of you volunteers to do the crank turning.
Stick it in there until it rests on top of the piston, and slowly turn the crankshaft by hand. Once you have that reference, then you can reinstall the distributor knowing that now the rotor should be pointing at #1 on the cap.
Once you get your motor cranked up and running, I recommend using a vacuum gauge installed at a manifold vacuum port (not a throttle body port) to check the timing. A steady vacuum reading means it is set properly. You can use a timing light too, but you will be surprised how much you can accurately adjust and diagnose with a vacuum gauge. This is why modern cars use MAP sensors; they can instantly give the computer a health report under any circumstances.
