This modified Dan Armstrong bass came up for sale in September 2016 with an asking price of $1,099 from deal Arbutus Music in Nanaimo, Canada. Seller's description pretty much captures all the changes - tuners, extra string holes, and also a changed switch along the way. This is likely a 1971 instrument as it includes a switch and appears to have the later sandblasted bridge plate. Sold for US$800.
"1970 Ampeg Dan Armstrong Lucite Bass, comes with non original hardshell case.
Previous owners had holes drilled in the headstock in an attempt to convert this into a guitar and the original tuners were replaced. Holes were also drilled through the body trying to make this into a long scale, through body bass. Other than those two things the bass is in great shape."