Pick up a Haynes manual for about $20 and it actually has a decent write up on the process. As for TDC, I believe the pointer on the balancer at the 12:00 position is an indication of #6 or #1 TDC. So if that is pointing up, you have the crank where it needs to be.
I one reads the GM service manual, they would find this info partially incorrect .
Yes cast pointer up is 1 and 6 TDC ,however, this is not the best position to remove the oil pan as the crank counterweight interferes with pan removal .
If the cast pointer is facing straight down, the gap between the counter weight and the crank pin is down, affording the most clearance to re&re the pan .
So as per common sense AND
the factory service manual ,
The best position for pan removal in the car is
Cast pointer on hub down (6 o'clock) which is cylinder 1 & 6 BDC
The one problem with the LT1 is the hub is not keyed and , although not a functional problem , it can be miss positioned and often is when crank seals or timing chains are done. Then the cast pointer can not be used as reference.