Not a direct bolt in at all. Although they look nearly identical, damn near everything that would bolt to your chassis/driveline is different. The motor mount on the 63 has four bolts/56 has three. The bellhousing on the 63 is smaller than the 56. The flywheels/flexplates are different. The exhaust manifold ports on the 63 are rectangular, the 56 are round. I did a similar swap into my 55 but changed the whole driveline. I feel it was worth the effort/cost but it is fairly involved. Try searching for engine swap or open driveshaft conversion posts. This topic comes up from time to time and there has been some VERY good info put up on this. Good luck.
