87 gmc sierra timing

[87gmcsierra]

Hello everyone i got a 87 gmc sierra with the 5.7 350 and was checkin the timing the other day because i could hear it pinging and it wasnt even on the scale it was off about a inch from it to the left , i tryed movin it a little to see if it would get to the mark but it would get way off wack do you think its 180out maybe?If i was to take the distributor out i would need to get the number 1 piston commin down from tdc right? any ez way to do this Thanks .