It's the series of engine and odd bolt size and angle that hold the sale off. To open up the bolt size is easy, to adjust the angle isn't so hard ethier but it is a pain for the do it yourselfer.
I hope someone with the 64/65 heads bought this . It would be a shame to butcher it, Nice piece , wish I could have afforded it . I have a Eddy D4B I need to clean up because a moron painted it silver.