Why not stroke a new Hemi? There are all sorts of stroker kits out there for the new hemi now. The more popular stroker kits give you 392 cid or 426 cid of displacement.
The one question no one has asked is why not stick with the 360? The 360 is a great motor in an A-body very easy to get over 400HP and 400 ft-lbs of torque, they will get decent gas mileage if set up correctly and can push you car into the 12's with little effort.
If I were you and was looking to make a hot daily driver I would stick with your low mileage 360 and put some sort of OD tranny behind it.
Oh Yea, I am you!! Already did that :)
I have a 360 that is making ~370 HP gets 17-18 mpg in daily driving and 21-22 on the hiway. I have run a very very traction limited best of 13.7 in the 1/4 with an A833OD 4spd and 3.55 gears. Its in a 68 Barracuda and the car has been my daily driver from April to November since 2000 and has had the 360 in it since 2005 (23k miles so far).
The 408 would be nice but I don't know if the fun factor would go up enough to warrant the hit in gas mileage.
