Balancer timing marks

I have a 55 chevy that I bought a new Chevy 300HP 350 crate motor for(part #

12355345). I put it in and put a zip tie down the #1 sparkplug hole and check for approximate top dead center. I put the distributor in and pointed the rotor to #1. The engine almost fired immediately and I tried to time it using the timing tabs I bought for a 6 3/4 balancer. The timing mark on the balancer was no where near the tab marks but it ran great so I broke the engine in for about 20 minutes. Looking on the net I guess they mark babancers differently. There is a mark at the 12:00 position on the timing cover that is stamped in. When I put the balancer mark with this mark on the timing cover it runs good. Is this how they time these types of engines? If you match this mark with the mark on the balancer is it at top dead center? The distributor I am using is a Mallory Unilite that has no vacuum advance. The timing for this engine is supposed to be 10 degrees BTDC at 700 rpm.