Seems like J Neck-d P basses are fairly common. Anyone reverse it and put a P neck on your Jazz Bass? Not exactly that, but 1 5/8” rules:
I have precision neck on my jazz bass. It's been defretted. But, it's only on there because I put the jazz neck on my precision.
P neck '73, J body '73. Precision neck shape from this era is most comfortable to me and most of my other Fender and non-Fender basses have that profile. J pickups don't do the P tone and punch but they are so versatile for other things. I'd do this again without a second thought. I have a P when I need a P and I have a true Jazz that I like but the P neck is my happy place. Something for everybody so find what works for you. Pretty sure there are some threads on P neck J mods.
For a while I had this sweet honey of a neck on one of my Jazzes and loved it! I agree with Killing Floor completely. And this neck is also a '73.
Whenever a B neck Jazz Bass comes up for sale I am broke. So I always end up building a J Bass with a P Bass B neck. I loved my 69 Jazz bass - I did 1000 shows on it between 1983 and 2000, but the skinny neck was the one thing that bugged me. Currently Jazz Bassless so the hunt for the Jazz body - 1 5/8" P neck is on again. Just like Sting. Last one pictured below:
I've got two! The black Jazz is a 75 with a 66 neck. The ash one is a 72 body wth a 65 neck. Both fretless
'72 Jazz body, 7? 1-5/8" Precision neck. It's been this way since about 1976, will stay this way 'til I die. I have big clumsy bass-player fingers, Jazz neck is just too narrow for me.