I pointed a light at the timing today, it's rather all over the place.
I timed it with the advance unplugged (capped on the carb), at roughly 1000 RPM. That was the steadiest RPM

The timing mark wandered around between both ends of the serrated timing bracket.

The distributor is new (2 years old, but zero miles) what could be the problem?

If it matters, it was a Snap-on digital timing light.

I'm no expert, but I read a post on here yesterday that said a stretched timing chain can cause this?

^+2

That's indicative of a stretched timing chain.

So, what's the difference between the $30 timing sets and the $300 ones? Intended to be a daily/weekly driver.

just get a good quality double roller timing chain with steel gears like what's available from cloyes

Before you open the engine, check the springs and weight in the dizzy. Make sure they're hooked up and not broken.

Worn/weak mech. advance springs, loose weight bushings, etc will cause the wondering timing, so will a timing chain with too much slack.

I would check the dizzy 1st.

ZS10, Knight Rider I hope you guys are right, but I've less than 1 hour on this dizzy. We shall see tomorrow.

What dizzy is it? The advance curve rate could be set too quick (low tension springs) and just not able to hold steady as it's trying to add mech advance in while it's just at an idle.

what kind of ignition set up are you running? If you are running an MSD box that will make the timing gun jump all over till about 3000 rpm when it start to fire one spark.

That sounds like too much wandering to be a loose timing chain. My old truck would wander the timing about 2-3* and it had the original timing chain with 240,000 miles on it.

For openers, see if something is wrong with the centrifugal advance mechanism, also pull the distributor to see if the gear at the bottom is getting eaten up.

Do you have an MSD ignition box on this setup?

If you're using the light springs and idling at 1K rpm, this may cause the distributor to start it's mechanical advance, giving you unsteady reading. This happened to me. Try a heavier spring just to check.

Did you bring the rpm's up to see if they stabilized at full mechanical?

I'm like Damon here, I don't think a stretched timing chain is going to make that much variation. IMHO.

I have a Mallory box, had a MSD unit and use an old Sears light. It's steady at idle with these multi spark units, my old Sun light was not.

Just another thought outside the distrubutor thing. You've yet to tell us about what the engine is. Flat tappet hydraulic, roller? The reason I ask is that a friend of mine installed a retro roller cam into an 80's sbc. We used all matched parts (Edelbrock), pushrods, roller rockers, etc. However after startup, we tried to set the timing, but it would not sit still, just like in your scenario. When we tried a little accelerating, thinking it may be chain slack as well, the timing would advance slightly, but then retard itself for a while, then advancing, etc. We couldn't for the life of us figure out what it was. We later learned that we did not have a cam button installed, and the cam was walking in and out of the bore ever so slightly, which changed the angle the cam drive gear as meshing with the distrubutor gear. We installed a nylon cam button, and dented the stock timing cover in slightly as to remove any play. The timing issue was solved, as least until the bushing wears out.

Harmonic balancer worn out and ring slipping. Seen it before also.

It's an OEM replacement ACCEL distributor. 59107
I'm not sure what cam it is, it was in the car when I bough it it there a way to tell? (short of pulling a lifter)
The rest of the tests will have to wait until next weekend. There's gas in the oil now, so I've got to get that straightened out first.

You can check for a stretched timing chain by pulling the plugs and rotating the motor back and forth by hand and looking at the rotor for delayed motion. I would try another timing light, I've seen a few dial-back lights that were grossly inaccurate.

It's an OEM replacement ACCEL distributor. 59107
I'm not sure what cam it is, it was in the car when I bough it it there a way to tell? (short of pulling a lifter)
The rest of the tests will have to wait until next weekend. There's gas in the oil now, so I've got to get that straightened out first.
Gas in the oil is probably the fuel pump if it is a mechanical pump.