Originally Posted by duxthe1

Yes the head will bolt but the 2.6 head has a squish pad and the 3.0 is an open hemispherical chamber. So a 3.0 head on a 2.6 would have a lot less compression. FWIW, there may be a few oddball assemblies out there but AFIK... no dice.

I wouldn't expect much gains from a head rebuild unless yours is in poor shape with excess deposits. Mercedes heads are pretty good castings out of the box but you may be able to get a little more out of it. Most of the work I did to my head was on the chamber side, the ports are hard to improve on.