"73 1.7 with 49K miles.

The idle rpm really drops if the car has been sitting out in the sun & not running.

Under cool & running conditions, the idle might drop by about 200 rpm once the engine is warm.

Is this "normal" behavior?

Is this the hot start issue?

Not familiar with 1.7 issues but the hot star issue is common to all. Once car is sitting in sun or recently turned off after running the starter solenoid imprudence goes up so is insufficient to start car. Easy fix with 80s Ford solenoid. About $30 and 15 minutes.
See thread by Mark Henry for instructions. Mine slid right in.

Thanks. Car starts but has a low idle.

Do you still have fuel injection? If so, what is the actual idle speed? These have an electromechanical vacuum leak (I assume the 1.7 uses the AAR too) that causes an increased idle speed when cold. Idle warm should be around 900 rpm. Is it going lower than that? I am really familiar with the djet 2.0 so I am not sure if your 1.7 has all the same stuff.

Right on. All original. Djet. Same warm idle of 900 rpm. Steady as a rock.

Actual out of the garage is about 1,000 rpm.

Thanks for the calibration point!!!

Idle for a type vi is very much dependent on the load, my idle is set at 1050, with the headlights on.

It can jump slightly higher, without the headlights and the voltage regulator switching off alternator load.

I set the idle at 1050 rpm because I run a lightened flywheel, the idle tends to dip very low on braking, works very well for me.

cold needs a richer mixture and more air, warm needs a leaner mixture. If your idle drops when warm could be that your air pressure sensor is leaking causing the car to run richer when hot. Could be other things, like the aux air valve closing like it should and therefore have to reset the cold idle to compensate. I would check the valve adjust the compression the distributor mechanica and vacuum advance retard mechanism evacuate the pressure sensor check head temp sensor hot and cold resistance the points dwell and the timing

I experienced the same prior to 123 distributor install. Now when I turn on the headlights, fog lights, fan the rpm (at idle) dips for a second then return to 1000 rpm.

Can anyone explain to me why load is an issue with the stock dizzy but not the 123?