Yep. Vintage Musicmasters were always Strat pups. That was the big difference between Musicmasters and Mustangs. The mustang used a small split coil (like a set of little oval P Bass pups) and Musicmasters had the covered Strat style pups. However, the "Vista Series" Squiers had the 4 polepiece pickups (shown in picture) that were designed for the bass.
Judging by the pics you posted, that Vista Series Squier seems to be a likely candidate for what this bass started out as.
Good Call DH!
