first, the nitty gritty. Chevy did everything that they did on that car for a reason. they PICKED pushrod over DOHC b/c they felt it offered them the best package of qualites they wanted in a motor.

1) pushrod engines are SMALLER than similar displacement DOHC motors. this allowed them to keep the LOW front hood profile they wanted.
2) pushrod engines are lighter, can be positioned lower in the chassis, and have a lower center of gravity than DOHC motors of similar displacement. This has obvious handling benefits.
3) there was no tradeoff as far as power production is concerned.
4) the transverse leaf suspension again allows them to keep the car as low as possible while maximizing suspension travel. The transverse leaf is actually a very ingenious design. It's very similar in function to pushrod actuated transverse coil spring dampers that most open wheel race cars use.

The only people that call into question the engineering of the c5/c6 are the haters that catch onto buzzwords such as pushrods/leaf spring/etc. They overlook all the amazing engineering that went into that car, hydroformed chassis (now the standard construction method for any production steel framed car with very high chassis stiffness goals in mind), the suspension that debuted on the 40th anniversary corvette, electronically adjustable shocks, could go from full soft to full stiff in a fraction of a second via varying viscosity electromagnetic fluid. Functionally the c5 was superior to anything in it's price range, period. It could hang with a 360 modena on a track (z06 could) for 1/4 the price. The c6 will continue that sort of price/performance.

Chevy engineered the c5 from the ground up. They looked at dohc engine designs and decided that for what they wanted to do, it just didn't make sense. They wanted torque, which means high displacement - you do a big v8 DOHC and it weigh a ton. If you make a DOHC small enough to where it can keep the same hood line & weigh the same as the ls1, you give up a lot of displacement, and there goes all your torque. Chevy is in the business to sell cars- the buyer for a corvette wants raw dog torque, and lots of it. So they had to comply with that no matter what, so low displacement high revs (ferrari) wasn't an option. The ls1/6 has one of the best hp/weight ratios of any v8 made today, but it constantly gets crapped on b/c it's a "pushrod."

sometimes what works best isn't the latest and greatest. props to chevy.