E320 to V8 conversion

[drmotorhead]

I am trying to find a nice E320 wagon and intend to get more hp out of it. It would be easier if I could get a wagon with a v8 already in to, but it appears mercedes never made them with a v8. I need the space of the wagon.
I know I can get the motor/trans from a 500sl for around 4-6k depending on condition, but how hard is it to get the v8 in there? I know mercedes did it on the 500e, but were there major changes to get it in there.
I suppose I could get a the 4.3 v8 instead of the 5.0, would that be an easier transplant?
Thanks!