I dont think the heads are anywhere interchangeble. I wouldnt attempt it anyway. Would actually be more cost affective to just remount your VG30ET and mount a second turbo, to make it a VG30ETT and get some head and upper intake work done.
Thats if you dont go and try and wedge that VG30DETT in there... not going to say you shouldnt try it... hell I am still working on my VH45DE swap... finances are holding me back.. got everything ready to go. Just ran out of cash... damned economy.