Whats everone working on?

was wondering if any one has done the head swap on a /6 that includes an Austrailian /6 HEMI head. Ive heard they perform like a 340 but with much better gas mileage.
I hate to take two steps backwards into the 70's and 80's when eveyone was crushing even the finest types of MOPARS because they didnt know they'de be valuable and because they could compare their gas consumtion to the 70's and 80's cars.....but I use my mopars daily and can no longer afford the gas. So, im considering unusual things like hemi-/sixes to 4 cyl. diesel or even salvaged hybrid power plants.
Anyone care to comment on the validity of such things? NOTE: I already know the invalid.