It is not 'bolt on'. There is some wiring that needs to be done, possible changes to the fuel system and welding in a bung for the O2 sensor. Also, I didn't read the entire manual but you will need to see if it can support your kick down linkage.
One big overlooked item to concider on these efi systems is that they require a new fuel system capable of the pressures necessary (~42-50psi vs6-10psi) . Not overly difficult but not an insignificant cost or amount of work. Some companies offer the kits with a fuel system or I've seen surge tanks with booster pumps as well; many will require a return line as well. From the people I've talked to I've had one person say that the edlebrock efi is not as good as holly or FAST; he didn't give reasons for it really though and was using his stuff strictly for drag racing.
For someone thats decent with mechanics (wiring) it would be a pretty straightforward install. There are even clamp on style bungs for the 02 sensors that you can get if you dont have access to a welder. (I was skeptical cause they look pretty janky but apparently they work reasonably well.
But it will bolt on (as long as your on a 4 barrel carb flange), it's not nearly as simple as bolting on a good carb though.
I've been waiting to see how the Holly sniper efi reviews once it's launched. Seems like a great budget system.
I have an Edelbrock E-Street EFI system with the Universal Sump Kit (returnless style), but it's still in the box in the garage waiting for me to get some other things done before I can install it - the main thing being the O2 sensor bung welded onto an exhaust pipe after the headers.
Once I get that done, I'll post a write-up... but it might be a few months away still.