The 3rd picture in the series shows the relief work required to fit the tappet guides in place. There is also some clearancing of the fins to fit and align the pushrod tubes.
The 4th and 5th images illustrate some of the mods on the pistons. Although I'd planned this thing using as much foresight as possible the piston lightening was done after assembly of the bottom end as I didn't like the notion of the 1/2" crown thickness. We live and we learn.