* Modify or replace the engine bay: The 572 is substantially larger than the stock engine options for a '65 Chevelle. You'll likely need to modify or replace the firewall, possibly the inner fenders, and potentially even the radiator support. Clearance issues with the steering components are also common.
* Custom headers and exhaust: Finding off-the-shelf headers to fit a 572 in a '65 Chevelle is unlikely. Custom-made headers will be necessary.
* Transmission and drivetrain modifications: The transmission and associated components (driveshaft, rear end) will likely need upgrades to handle the immense power of a 572.
* Suspension modifications: The added weight of the engine and the increased power will likely necessitate upgrades to the suspension to handle the extra strain.
In short, while it's *possible*, it's a substantial undertaking requiring significant fabrication, mechanical expertise, and a considerable budget. It's not a project for the faint of heart or inexperienced builder.
