4.3 timing mark

just finished a engine changeover and need to install distibutor. I looked at balancer and noticed two marks. which one should I use to set TDC? The engine is in place and using a compression gauge to check for compression stroke may be difficult to install into head. Suggestions..??:rofl:

I too, need to install a distributor in my 4.3 Astro. Did you ever find out which marks to use?