Hola Slowoldguy ,thanks for the pm.
Sounds like the makings of an excellent ride and with an excellent strategy.
Here 's a another suggestion for route you might work in as you progress south on Mex 85.
When you get to Jacala HGO , ( that is south of Tamaz' about 100km) consider taking the GRAVEL road west out of downrown Jacala. This is a great route about 30km to village of Pacula. There is a DRY river crossing at the bottom of the valley , but if there has been recent very heavy rain and the river is flowing you may have to turn back. This is why I suggest starting from Jacala which is only about 18km from that river and you would not be annoyed by having to retrace your short road to Jacala .If you approached from the other direction such a flooded river would force you to retreat over more than 100km.
The gravel road section to Pacula winds down and up across the rolling mountainscape ranchlands,
. In Pacula the route turns south and is a great scenic paved mountainscape road that rejoins Mex 85 north of Zimapan(shows in red on your map). Last March in Pacula I heard also that a new connection road is being opened up to join Mex 120 to the north ,near Landa de Matamoros, that should be really interesting too.
I keep glancing at your map segment and see that it is missing a lot of the really useful town names and does have some misleads. For instance on Mex 120 south of Jalpan de Serra there is nothing showing the town of Pinal de Amoles.... a big miss with hotels, Pemex etc.
.... but it does show the much smaller town of COMARCO at a junction between Mex 120 and another road which it implies is of equal quality and runs north into the Sierra Gorda to join Atarjea and Xichu.
THAT is a road you guys MUST DO ! .... but it is NOT PAVED . It is a wonderfully winding gravel road over the mounhtains ,some farms It joins the Atarjea road about 10km west of that village. They were working on paving the road from Atarjea to Xichu this past April and I had to follow the detour in the actual riverbed. Gas available in Pinal so fill up for the day , also gas in Xichu ,Santa Catarina , Victoria, Penamiller. I am sure you have other more detailed maps to actuallly use in the field.
From the Atarjea road there is another winding scenic gravel road connecting south across the mountains to Santa Catarina which becomes excellent pavement not shown on your map to los Molinos and Sta Catarina
In Santa Catarina ( 2 hotels) stop for a meal at Restaurant El Indio and say hi for me to my friend Gustavo and his family they put on a gresat breakfast lunch and dinner.Just ask locally everybody can direct you to it.
From the Atarjea all the way to Xichu is also still gravel, then pavement all the way west to San Luis de la Paz. From west of Xichu a cross mountain road connects south to Victoria.
You definitely need a more detailed map- yours does not even show Bernal
A neat side trip east off Mex 120 is hinted at only by the red line to "Ranas Y Toluquilla" DO take that side trip. It is wonderful scneic paved highway up into the oak forested mountaintops to the town of San Joaquin ,hotels and Pemex- fuel up! and from there a paved road can take you right down to the river border between HGO and QRO and back. and another gravel road wends north into the hills to more smaller villages.
So much to explore.