Can I use a non locked axle shaft?
Yes.
That is why I say it makes more sense financially to just buy a non-locked axle assembly. Why buy an e-locked axle, then gut it to install an ARB locker. Last time I checked, non-locked axle assemblies were selling for about 1/3 the cost of an e-locker axle.
I'm still a bit confused about what you are trying to accomplish. Can we clarify a few things so we can give you the best advice?
You have an FJ45.
Planning for 37" or bigger.
You are retrofitting 80 series axles under the 45. Front and rear?
Makes sense; 80 series = full floater, 63" width, 30 spline. Do you already have the axles?
You obviously plan to wheel this thing, but are concerned about the twisted spline potential of e-locked axles. Right?
You don't want Chevy, Dana, or aftermarket axle assemblies. Right?
If you already have the e-locked axles, your choices are:
Run 'em as is.
Upgrade the axle shafts such as machining splines, or aftermarket chromoly shafts.
Sell them and recoup some cash to buy non-locked axles and then install aftermarket lockers.
Sell the e-locker third, modify the axle assembly for a non-locked third and axle shafts, buy non-locked third and axle, then install aftermarket locker.
If you haven't bought the axles yet your choices are:
Buy non-locked axles, then install aftermarket lockers.
Buy e-locked axles and run them as above.
Buy e-locked axles, sell the e-locker third, modify the axle assembly for a non-locked third and axle shafts, buy non-locked third and axle, then install aftermarket locker.
The last two scenarios on each list seem to be what you are asking about, which would not be the choices I would prefer.