new timing light = new questions.
 

I shot my timing tonight with a new timing light I bought, and I adjust to TDC, then back off for my grade of fuel (89 right now) as I liik at the timing mark (|), or a ZERO intersected by a line (correct??)
it fluctuates by 3-4 degrees ATDC. Turn car off, re-start and it fluctuates wildly between TDC and a mark stamped 27|0.

It's time to replace a timing chain, isn't it?

Assuming I'm checking with the correct mark. M117.986 (1978).

Getting a timing chain will be no problem for me, BUT I'm going to have some difficulty getting the guide rails. can a new chain be rolled in without having new guides RIGHT AWAY, and do the guides later?

Jumping timing sounds more like a mechanical advance gone wild or a loose rotor. The timing chain would not jump around between the cams to make the timing show fluctuations, it's only loose after the tensioner whether it's new or ancient.

You can roll in a new chain on old guides but I wouldn't recommend it if they aren't the aluminum ones.