hi from french mopar owner

Welcome. Beautiful car, and most here would be very happy to have your current paint and interior.
Before you go V-8, lookup some of the posts on adding a turbo to a slant w/ amazing performance, but you must be very handy to do that.
Many, many posts on converting from a slant to a small block, but it isn't trivial. Most end up changing almost the entire drivetrain, rear, suspension, and brakes.