If you're going to use the 305E bellhousing you'll definitely need the right 8 bolt flywheel for the 478. There were early 8 bolt flywheels used on 62-65 6500 series trucks that were the correct diameter and if you got a hold of one of these it would require machining an adapter to accept the smaller light duty pilot bearing because the hole in the center is much larger. The other alternative is a 379 flywheel if you can find one which is a straight bolt in. Myself I went with a custom flywheel from Tilton Engineering and of course it was balanced with the whole rotating assembly of the 478M, a good amount of weight was added to the flywheel. Another issue I need to bring up is Tilton never machined the flywheel surface facing the engine block to clear the four bolts that bolt the bellhousing to the engine block, that machined relief area is very evident on a 305E flywheel. I ended up grinding down the heads of the 4 bolts to achieve the right clearance
Here's a pic of my custom 478 flywheel