It doesn't matter. Start it up and set the timing with a timing light and you should be good to go. If you have issues with spark scatter then drill a hole in the cap next to the #1 tower and confirm rotor phasing with the engine running. Some of those Mopar electronic distributors were designed wrong and under full vacuum advance the rotor would point between the towers and the spark would jump to the wrong cylinder.

18 is fine. put the dist. in see which tower its pointing toward, that's number one. adjust the dist. housing to line up the reluctor/induction coil. and snug down. fire it up.

18 is excellent. pics are correct: rotor at 5 o'clock/reluctor dead even with the magnet no matter how the slot is clocked but in this case it is parallel which that is a good starting point & is correct most of the time. EDIT some dists have different bottom tang to rotor clocking

Update! I FINALLY got to try starting my engine today after many delays. As mentioned, timing was set at 18 degrees bdtc. To my delight, it fired right up and ran smooth. I set the carb at 2000 rpm and per the cam instructions I fluctuated the rpm between 2000 and 2500 rpm. Everything was going great. About 10 minutes in, it suddenly started overheating badly. Steam was pouring out from under the radiator cap and it actually blew the overflow hose right off. I have a thermostat (new) installed and the radiator is from my other car and has never had any issues. I ran all water, no coolant. I guess I will take the thermostat out and try it again.

I set the timing up the same way but I'm not sure if the ECU fires off the front of the relucter wheel point or straight on or off the backside of it
I set the timing mark on the balancer (after verifying it is accurate) at 15 BTDC and then align the reluctor with the pickup edge and start he motor up and verify the actual timing with a good timing light right away and adjust if needed

Ditch the thermostat, try again a fan blowing at the engine compartment/grill is always helpful.

But that being said at 10 minutes the cam is probably broke in.

Did you check the timing during this time?

No, I didn't check the timing. It was running so smooth I didn't think the timing was an issue. The engine is not in the car, it is on a dolly. I had a box fan blowing through the radiator and a couple of fans blowing on the sides of the motor. I tried running it again a little while ago without a thermostat and it only took 6 minutes to overheat this time. Again, with straight water. That being said, I think the first run with the t-stat I had in it it appears to have been a bad t-stat. Couldn't get it to open doing a test in a cup of boiling water. I am going to get another new t-stat to put in it. What temp t-stat should I get, 180 or 195?

180

But it should cool without a thermostat.

I was just curious how close you where on the timing.

What kind of fan on rad? Any shroud?

I didn't mount the fan on the motor so there is no shroud. I put a house type box fan in front of the radiator. This afternoon I put a new 180 degree thermostat in. Haven't run it again yet.

If the timing is to retarded it will cause the coolant temp to rise quickly and significantly. Advance it some and see what it does, easy enough to try.

I advanced the timing some to about 22 degrees btdc. Haven't had a chance to let it run more than 5 minutes or so but it didn't overheat in that amount of time. In regard to setting the total timing, do I understand this correctly? Set the initial timing (as I now have) then turn the idle up to 3000 rpm and set the timing to 34-36 degrees btdc? Also, what is the typical idle speed setting when running a cam that has more duration than stock? My cam is rated at 234/242 @.050 and LSA is 110.

160 Especially for street use

If it cranks/starts OK at 22 BTDC when hot I would limit the total (checked with vac adv (if used) plugged) at 34-36 with the FBO plate.

I always set the total timing at 3000-4000. Usually with one hand on the throttle and the otter holding the gun (or get a helper).
If you have 20 min run time its broke in.

The more initial you have the happier it will be, and as stated limit the total advance when done. But give it all the initial it wants/needs. Most racecars have the timing locked out, so they idle in the 30-40 range.

Big cam, low vacuum, I don't even fool with it or band-aid around it. Lock it out and use the electronics to retard it as needed, when needed.

Street car, small or stock cam? Sure.

Watch the valves. As the engine rotates, the intake will open as the piston travels down on the intake stroke. As it reaches BDC the intake will close. As the piston comes back up it will be on the compression stroke. At TDC, drop the distributor shaft in it correctly and set the distributor in with the rotor on #1.

I had this same problem breaking in a cam a long time ago, my headers turned cherry red and it boiled over. Found out later about the timing issue causing it, once you get the engine running and you bring it up to 2000 RPM throw the light back on it and adjust the timing so it's at 34-36 degrees and run it there. Most distributors mechanical advance isn't high enough at 2k unless you've modified it yourself. Next cam I helped a friend with he saw the samething, fired it up and the headers were staring to glow at 2k , advanced the timing and the headers stopped turning red.