If you have to replace your Q-jet, you're lucky in that you have multiple options you can go with. I would replace the intake at the same time, but you still have options with that as well.
If you want to stay with your stock intake, then you have to look for a spread-bore carburetor...otherwise you'll need an adapter which is tall enough to create hood clearance problems. Holley makes a direct fit Q-jet replacement carburetor for a stock intake...it bolts right on and everything connects the same...linkages, fuel inlet, etc. It's a different shape than the Q-jet, and you'll need to either eliminate the EGR valve or get an adapter that moves it slightly so the new carb doesn't hit it.
My own preference for a street car is the Edelbrock Performer carburetor...your car would use either their 600 or 650 cfm models. These carbs are very simple, easy to adjust and hold their adjustments. The potential downsides are you need to do some adapting for the linkages, cruise control, and fuel lines and fuel filters. None of those are a big deal. but just something to be done. The bigger and more expensive downside is you need their proprietary solenoid for air conditioning that maintains the idle when the a/c is engaged. It's somewhere abound a $100 addition to the cost of the carburetor itself. Again...an easy install, but something to keep in mind.
Holley and Demon each make great square-bore carbs (as is the Edelbrock), but being subjective, I think they're better suited for the track than the street...my opinion and my bias. Others will feel different.
For an intake, I think the two best options are either the Edelbrock Performer, or the Performer EPS. The standard Performer is for both square- and spread-bore carburetors...a bit of a compromise but still excellent intake and better than the stock unit on your car. The Performer EPS is for square-bore carbs only and is optimized for them. It has somewhat better horsepower and torque ratings than the standard Performer...not by a whole lot, but better as it's not a compromise design. Edelbrock also makes other intakes, but most, if not all will cause clearance issues with a stock Corvette hood, unless you use a drop base air cleaner or a higher hood.
There's other quality intakes as well...Weiand for one. Summit Racing sells a clone of the Edelbrock that's made offshore, but the difference in cost is minimal. When it comes to intakes for a small block Chevy, Edelbrock pretty much has the name, performance and the market.
I had a '78 L82. I installed an Edelbrock Performer and used the stock Q-jet. I was very happy with the results...it was much more responsive and stronger. That combination never caused me a problem of any kind as long as I owned the car.