I have had the GSG board for more than a year now, and finally got the parts together to build it. I will be using James 6112 OPTs (tctubes.com) and the PA774 (dynakitparts.com) as the PT.
Tubes are monoplate Sovtek 6B4Gs from ebay, new issue Tung Sol 6SL7GT and generic 6AX5.
The top plate was fabricated by Front Panel Express. Here are some pictures:
Instead of a chassis to hold the plate, planning to use wooden pillars with cones at the bottom.
Should be ready in a week.