We don't register tags where I live, we register the vehicle. Anyway I don't know what the issue would be in TX about heirs. In my state they would take the title and the will to DMV, get title in their name and then sell it. As far as a buyer goes, they would be comfortable if the title serial number matched something on the truck. Now is the time to get that done.
It won't be the first time TX DMV is told that back then they used the motor number and motors get replaced. The procedure lies with them. Your actual questions have been answered. I'm sure you will get it worked out with DMV, but as said, don't do ANY self numbering. Present the situation as is.

Some of us have no idea what this means " I am going to register my 1950 Texas Truck tags tomorrow, the tag is clear. get a 5 year sticker and no inspections. last registered in 1992, so it might not be in the system any more."

The word "tags" in some states means license plates. In my state it means a sticker in the corner of the plate to show expiration date of registration. When well sell, we keep the plates, sign over the title and the buyer gets new plates with a new plate number.....and a new title. VIN stays the same of course.


Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn