Pretty easy to do. Did you pull the distributor and lose (or never marked) your original orientation? If so, take the valve cover off. Using the crankshaft pulley, turn the engine clockwise and watch the intake and exhaust valves on #1 (front of engine) and #6 (rear of engine). Once you observe #6 intake and exhaust valves moving up and down in sequence with each other as you rotate the pulley clockwise AND you see that #1 valves are not moving at all, you are close to TDC. There will be about 5 or so degrees CW and CCW where the #6 valves are slightly moving. Move the pulley back and forth until you get more or less in between the point where the valves are showing to be closed. Then #1 is at TDC and you are not 180 degrees out. Regarding the distributor, you can start by observing the slot in the oil pump shaft and see where is is positioned. Rotate it with a long screwdriver to about the 1 and 7 o'clock position to start. Take the distributor in hand and with the rotor pointing at about the 8 o'clock position, insert the distributor into the block. As the distributor gear engages the camshaft drive gear, it will rotate slightly CCW towards the 6 o'clock position. If the pump slot is in the proper position, the tang of the distributor shaft will drop in and the distributor will seat fully into the block. If the slot is not in the correct position, move it slightly from the 1 and 7 o'clock position CCW or CW as required until the distributor fully seats. Always start insertion with the rotor at about the 8 o'clock position. You may have to do this several times. Be patient. As truckernix stated, the normal rotor position for #1 is at a 90 degree angle to the block facing the right fender. Hope this helps. Just did it to my rebuild after much searching.
