Cough! cough!
...have you considered the LS series engines?
Just a thought..
LS7 in one of these would be worth considering & tough to beat.
Benefits include...
Small, light weight package (thus may reduce fabrication costs for install?).
Full alloy block, most parts forged, 6 bolt main caps, titanium rods, etc...
They produce stock out of the box about 500hp 470lb.ft. Rev to about 7K rpm get great millage & run on pump gas.
Like I said tough to beat...
Of course you'd have to keep the bonnet closed if you ever went to a show for fear of being ridiculed... but as a daily driver... trophy hunting at shows is probably not really a consideration for you