Not very practical with a 283 and be very drivable. The 283 was available with power pack heads and 4 barrel carb for 220hp back in it's day. It can make respectable horsepower with the right parts selection, but it's going to be a high winder when making that kind of horsepower. IMO 300hp would be really pushing it and retain some drive ability. If I was trying to keep the truck true to form I would give it a good rebuild and make a Power Pack out of it, those parts are easy to find and cheap.