well it sounds very ambitious and complicated but no doubt you have looked into everything before deciding to go the 3.4 route.
A couple of 3.4-specific questions for you:
where did you get your cams modified and what specs did you decide on? Did you pick the specs or did some shop and if so, who? As far as I can tell
nobody has actually GOT modified 3.4 cams yet (PFF or 60*6 etc) so this is a first!!
the other item is what are you doing about con rods in particular (and maybe a crank, too)?
The bottom end of the 3.4 is somewhat known (according to local wreckers, anyway) for opening 'side doors'. I don't know if it is the rods or the oiling system (pretty convoluted one at that) or the crank/bearings or all of the above.
But good luck and keep us posted!