Vintage Dirt Bike Q & A

I'm helping my dad out with this one. He recently obtained a Montesa Texas and neither of us are familiar with them at all. This is out of a storage building he owns and is disassembled and missing some parts (headlight and associated wiring, clutch and brake cables). The motor is also locked up.

Right now he's debating on what to do with it (sell as is, rebuild, part out, etc.) but the fact we know nothing about it hampers that. I've been trying to do some research, but I'm not finding much in regards to this model.

Any help out there regarding value, as-is vs running, or potential market for parting out? SN is 12MXXXX, which I believe makes it a 175 model. As I understand it, this is a pretty rare bike, and I believe it based on how difficult it is to research and find parts for if he does decide to get it running again.

Any help at all would be awesome.