timing 5 degrees after top dead center?

Just bought a '70 Ford F-100 with a built 351 C, comp cam 268, breakerless distributor, MSD Blaster coil. Just noticed the timing mark is at 5 degrees after top dead center. Could this be correct? I'd like to check it with a timing light but I need to know if I need to disconnect the vacuum advance and plug it up in order to check the timing. Can any one help me out with this?
Thanks

Usually the only way to be sure about ignition timing is to check it with a timing light.......and yes, you do have to disconnect the vacuum advance for an accurate reading.

Thanks,

It's been a long time since I worked on anything this old.

Something is not right with that. normal timing at idle should be between 5 and 15 degrees BEFORE tdc. If the balancer is old and an elastomeric type, the outer ring could have slipped meaning you will never be able to time it correctly, and that the balancer will not do it's job well. Buy a new damper, then time it.