A cute little critter, and an interesting design. Maybe I will run across one some day.
I guess the sync chassis was the one piggybacked to the side of the CRT.
I would volunteer to help your uncle straighten up his attic, and dig like crazy in search of the missing parts. The sync chassis seems like an odd thing to remove -- what else would it be used for -- unless you are a teenager just fooling around.
Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html