I've got this cheap bass kit and turned into a Mustang bass look alike.
There was a J route at the neck position but the cavity was plugged then I've cut the headstock with the same contour as my Musicmaster bass headstock
Yes I've used a jigsaw. Didn't turned out perfect but I don't mind.
I then sent the body and neck to MJT and they killed on the paint job.
Bill helped me with the bridge and tuners and control plate (thank you so much!!), the knobs are original 70's Mustang Ebay that came in with newer pots. Dunlop straplock buttons and an old string tree I've had. The pickup is from a righty cheapo Mustang I used to have but I'm going to upgrade it some time soon.
The pickguard came from WD customs but I've had to cut the neck pocket in order for the neck to fit in and also had to cut where it meets the control plate but came out okay.
I've only sent this bass for a paint job because I've had the bass put together long enough to know it was a really nice bass to play and sounded great as well.
Big plus for me, the body is mahogany! Notice the bridge is pushed towards the middle of the body that is because the body is a little bigger than the real deal one. But it's a 30" scale.