On the front of the timing chain cover, drivers side towards the top of the harmonic balancer.
There is a mark on the timing chain cover behind the harmonic balancer(behind the crank pulley). The harmonic balancer also has a slot cut in it so that you can line the crank up with the mark on the timing cover. The mark on the timing cover should sit at the 2 o'clock position or the 12 o'clock position. My 96 Chevy 305 is at the 2 o'clock position.
That would be the biggest and widest mark. Are the first mark on it when turning it clockwise to the pointer.
6 or 8 drgee
There is no timing belt on a 305 unless it is an aftermarket belt drive system.
same as a 350
6 degrees BTC
The easiest way is to look at the Harmonic Balancer. The 305 has a wider thicker balancer than the 350. Pus the timing tab on a 305 is located ON the timing cover and the 350 is bolted on the with the cover bolts. Riky9
8 degrees.
32 degrees
counter clockwise.
6 BTDC