MIM conversion is it possible?

Yes

 

There is absolutely nothing to stop you from upgrading either the hardware or the electronics if you wish to. MIM Jazz basses all have pickguards, but if you get a replacement, be sure that it's compatible. There are several flavours of Jazz bass that have pickguards with different drillings. The knobs are attached with a simple screw, and easy to change. The bridge is perfectly functional, and there is little advantage to upgrading it other than for looks, but some prefer to do it anyway.

 

Are the neck pocket dimensions identical for MIA/MIM?

 

In my experience, yes.

 

I've swapped many Fender and Squier necks and they all fit like a glove!

 

All of the hardware can be easily upgraded but make sure that you get a pickguard that is specifically for MIM jazz bass as the screw holes do not perfectly line up between MIM, Squier and USA models

 

+1

 

OP,
I personally think a jazz looks funny with different knobs.
Someone put precision knobs on theirs and I almost fainted.
The same thing applies to the Mustang...057912

 

I had problems with a MIM bridge. A couple of the saddle screws slipped (it took 5 songs for this to happen) and the string completely fretted out. I replaced the bridge. Also the the plastic nut eventually broke outside of the g string allowing the string to slip out so I had a good bone nut installed. It ended up being a great bass.

 

The same thing happened with my MIM Precision. It would take a few weeks for the saddles to work their way down. I bought threaded saddles and that fixed it.
I actually like this bass better than my MIA.
Mine had CTS pots and the jack had been replaced. Put a Switchcraft jack in it if it doesn't have one already.
Pickups? That's a long and winding road to travel and it can get out of control for some of us.
Try different strings first. Some MIM pickups are fine as-is.
Personally I can't play a bass that hums, so I would probably put humbuckers in it. That's just me.
Good luck finding a pickguard that fits. I gave up and left the original white one on it.

 

So wait, this isn't a religious question?

Turns out it sorta is ...

 

Yup. I use mainly Squier bodies for builds and don't have to modify much. MIM stuff is a similar fit, so far as I know.

 

Don't look at mine then. I've got a 90's MIM with strat knobs and a one piece pickguard.

After years of looking for control plates and actual jazz pickguards that fit together perfectly I've given up and accepted the fate of having a one piece pickguard. I do have a set of actual jazz knobs that I'll put on if the mood strikes me.

 

MIM use Metric parts, so I'm not sure SAE parts will fit into a MIM controls-plate.

 

With a pickguard, it's easy, you just ream the holes, but different story with the controls-plate.