Okay,but let me give you a suggestion or two.
To shape the back of the neck with it attached,the most inexpensive tool you gan get that will work well would be a good wood rasp.A long one,because you will need the length to shape around the body join.
I hope you already have the neck face jointed,because doing that with the neck attached will require a certain level of skill with a hand plane.
I don't recall if you said what type of bridge you were going to use,but if you have not already decided,then you are going to have to try to find one with sufficiently low string height to allow for the extremely low body/fretboard ratio,since you don't seem to have a neck angle.I don't believe that you will be able to make a standard 1/4" fretboard work for that.Most times(without a neck angle)the BOTTOM of the fretboard is 1/8" to 3/16" above the guitar top,and that is to allow clearance for a RECESSED floyd rose....one of the lowest bridges you can find.
So you will have to choose carefully.I think you said last you were turning it into a bass?scale length problems aside for now,look into the Badass bass bridges.I am only slightly familiar with them,but i believe they may have a working height similar to a recessed floyd.
Now back t the scale length.You have enough neck length for the minimum 32" bass scale??(there may be a 30",I am not all that familiar with bass guitars..)
The thing is,playable stringed instruments are built to EXACT measurements as far as the playing surface goes.You can play around with headstock angles,string trees,body shape,pickup placement,and all that stuff to a fair degree...but you don't jack with the playing surface.