I have been looking around in my area for an XJ and have found several MJs.
Is there any disadvantage to building an MJ? I'm guessing an MJ has a frame.
Is the aftermarket support any good for that model?

 

No frame in the traditional sense. The cab and rails that the bed mounts to are "unibody" like the XJ. Other than that the only difference is one is a people mover (XJ) the other is a stuff mover (MJ). Both use the exact same drive train (trans, motor, suspension, t case if 4WD) and pretty much everything on the XJ from the front doors to the front bumper is the same (for a 4 door XJ)

 

I like the MJ's better than I do the XJ's.

From the cab-forward it is essentially a XJ with some minor differences(reinforced front LCA brackets being one) but from the cab back its a different beast. The leaf springs are longer and the rear axle is a "spring under".

Here is a pic of mine, i paid $250 for it in May 11, this pic was taken in July 11 after a complete resto-mod was completed by me.

 

So there seems to be no structural advantage to an MJ over an XJ.

Correct?

If so then I'll continue looking for an XJ to build since that's what I had in mind.

Thanks.

 

Not from the cab-> forward, the rear is a frame so to speak but not what you would find in a truck, its a boxed style with same gauge steel as the front of the uni-frame is

 

false. the entire uniframe is stronger than the XJ.