I am disappointed at your remarks, and I'm afraid your understanding of engine design may be incomplete.
When you write
, you must be comparing one DOHC engine to another. I can you assure you of a simple fact; a 5.0L OHV engine will always (and I do mean always) be substantially smaller than a 5.0L DOHC engine. It's simple design, the DOHC engine has 3x more camshafts, more timings chains, more sprockets, more lifters, more of everything. This stuff takes up space. Every piston engine requires pistons, rods, a crankshaft, that will be the same either way, but the OHV engine will be more compact on the top end.
As for
You really don't have to look farther than a comparison of LS1 f-bodies and mod-motor mustangs to realize the fallacy of your remarks. LS1 Camaros can get 30mpg highway when equipped with the T56, and make quite a good deal more power than the DOHC mustang engine. The reason the Camaro has more displacement is because the OHV engine allows for more piston bore and stroke length than the "sophisticated" DOHC design.
I hope that you haven't fallen prey to the import lover argument of "more HP/Liter", which is not taking into account the external dimensions of engines. The Northstar engine is dead, the small-block chevy lives on, that should tell you something. Put direct injection on a LS3 and you've given it another 10-20 years of competitive performance.