I'm sure that there are aftermarket products, and I have often heard of using chevy's RamJet system on big-blocks.
I did see a neat article in Car Craft (I believe) where they drilled holes into a regular carb intake manifold to put in injectors from a TPI system (like RamJet), then used an old carb as a throttle body. They were careful about the placement of the fuel injection rail and other parts so that you couldn't see any of them when the motor was installed, which I thought was really neat.
The key to tuning EFI is all in the computer system. You will need a computer that can comprehend the amount of fuel and air you are cramming into that big block. Most EFI systems can use the O2 sensor (something you will need to install into your exhaust system) to get the proper mix of air and fuel. Basically, the O2 sensor senses the amount of unburned oxygen in the exhaust, and then it adjusts the amount of fuel to match, so basically the big difference between carbs and EFI is that a working EFI system will automatically adjust the air/fuel ratio to compensate for real-world conditions.
If the system is put together right, it should give you a car that is more reliable and puts out more consistent power than a carb system would. The big drawback is that most people find a carb easier to work on than EFI, so if something does go wrong it can be a little more complicated to find.

Chris