^^Yup, made by Phoenix Engineering, which was previously Bird Engineering. I have a Bird myself.
Definitely a related model to the Baja, since it has the characteristic engine plate, engine cage, and factory differential.
Probably a later incarnation, because I've never seen a member of the Baja family with that cage.
Or it might be a Baja, but just a later version.
Assuming there was no major changes to the karts in the model lineup in the company's lifetime, we can safely rule out the Baja, Baja Magnum, and my kart as well, the Starbird.
The names may have changed when the company became Phoenix Engineering, but I don't know.
I'm not positively ruling things out or ID'ing your kart, but just giving all the info I know.
P.S - Couldn't find any old Sears/Montgomery Ward ads with your kart with an internet search.
Cool kart!

EDIT - It's also got a Tecumseh OHV engine. Personally I'd swap to a Briggs flathead, but that's a matter of opinion.