Well, although I'm quite partial to the LT5 engine, there are couple things to take into consideration.
First of all the ZR-1's LT5 engine was a joint venture between GM Powertrain and Lotus in Hethel, England. At the time, GM owned Lotus. Because the construction of the engine was going to be mostly aluminum, GM didn't have a lot of experience building all aluminum engines. As a result, they looked at several outside sources for manufacturing and chose Mercury Marine; a very well known, reputable outboard manufacturing company located in Stillwater, OK. The idea/concept of the LT5 engine actually began in 1985 as the Corvette engineers had the insight to realize that a very serious threat was coming from overseas. Hence, the LT5/ZR-1 project began.
At the time, a DOHC was the way to go to create the high revs and power necessary to push the Corvette into exotic car performance territory.
As the ZR-1 matured from 1990 to 1995, so to did GM's ability to massage more power out of the pushrod motor. Hence, the birth of the LT1 engine in 1992. The LT1 engine put out 300 horsepower; 75 hp less than the 1992 LT5. Even though the engine lacked the 75 extra horses, the LT1 powered Corvette also lacked some of the ZR-1s extra weight. Over the years, the ZR-1's weight increased to just over 3500 lbs I believe (see
http://corvetteactioncenter.com/specs/c4/zr1/zr1specs.html for exact details). The difference in performance grew smaller between the LT1 and ZR-1.
It wasn't long that the writing was finally seen on the wall: nearly similar performance could be had out of an engine with much less moving parts which cost much less to manufacture. As a result, the LT5/ZR-1 program was killed in 1993 as the last LT5 engine rolled off the assembly line in November 1993 (shedding a tear here....). The extra engines saw their way into 448 1994 ZR-1s and 448 1995 ZR-1s. The rest were stockpiled for spares.
The rest is history....the LT1 led to the LT4 and in 1997, the LS1; an all new "small block" pushrod motor unlike the previous generation small block debuted. For the 2002 model year, we have the LS6 and I wouldn't be the least bit surprised if the LS6 engine was capable of producing even more power with minor modifications. Basically, we have LT5 engine output coming out of a much smaller motor (in a packaging and number of moving parts standpoint) for much lower production costs. From a number standpoint, it just makes sense.
The other thing to keep in mind is that by nature, DOHC engines are not torque monsters contrary to popular belief. Their forte lies in their heavy breathing capability which is why the LT5 engine is capable of breathing as deeply as it does in the upper rpm range and propels the ZR-1 to its 180 mph top speed.
Although I haven't done a seat to seat comparison, I have heard many people state that the L98 engine actually felt more "torquey" than the LT5 engine. I wouldn't be surprised. The ZR-1 is certainly no slouch by any stretch of the imagination. It definitely produces enough torque to suck your eyeballs back into their sockets, but the "ole pushrod V8 engine is just as capable if not more than capable of producing that same kind of suction.
I highly doubt that we'll see another DOHC motor in a future Vette anytime soon, but who knows....
One of the cool things about the LT5 engine is not only the amount of enginneering and history that went into building the motor, but visually, it is literally an awe inspiring piece of engineering to look at.
I spent the better part of today cleaning mine. I had the hood up and a neighbor stopped by who was out walking his dog. I happend to be on the ground cleaning the inside of the wheels and didn't even know somebody walked up. All I heard was...."holy s**t, what the hell kind of motor is that!?" When I told him, he said that it was one of the most beautiful engines he had ever seen. His eyse were like half dollars as his eyes wandered all over the plenum and valve covers.
The engine has an extremely unique sound like none other I've ever heard. It has a more metallic, deep pitched howl upon acceleration and combined with the stock exhaust, really produces an amazine growl from inside the car.
Unfortunately, I have never had the opportunity to drive a Z06 Corvette....let alone a regular LS1 Corvette. I absolutely love the Z06, the concept behind it and its fantastic powerplant. However, in all honesty, I would not trade or sell my ZR-1 to get one (although I would have absolutly no problem parking a nice bright red one next to my Vette
). The 2002 Z06 can somewhat outperform the ZR-1 in some areas, but that's really not much of a concern of mine. For me, the joy is in the LT5 motor - a rare engine in the overall late model scheme of things that is extremely unique in its materials and construction when looking at the entire lineup of GM engines. I don't think we'll see anything like that again for many years to come.