Who else's car started out as a LOW option car?

I don't have a pic of the fender tag for my '70 Duster handy but years ago I did go through the build sheet.

318 V8
904 auto trans
A/C
Power steering
Front disc brakes
AM Radio (if that's not standard?)
CA-mandated ECS emissions junk (Cali car)

That's about it. Manual brakes, no console (column shift), standard suspension, 7 1/4" open rear with 2.76 gears, no passenger side mirror, manual foot-pump windshield washer, 2-speed wipers.

I'd say it's "medium-optioned"? The radio was gone when I got the car and one of the first things I did was gut the non-functioning A/C compressor and lines. Currently running a 450-hp 360 with a supposedly rebuilt (according to guy I bought it from) 904 and homemade shift kit (removed some check balls and enlarged some holes in VB separator plate). Upgraded the K-H front discs to '73-up BBP ones but still manual.

That tired 318 was a pig at 8000'+ elevation where I lived when I first got the car, can't imagine a slant-6. Made it easier to swap to a 360 as well already having a V8 K-member.

Despite being a few model years apart, outr cars seem to have been optioned identically (aside from the California emissions stuff). IIRC, unless something changed between '70 and '73, yours will still coded with an "L"/"low price class" VIN. I think your "medium" descriptor does make sense though.