Here is a parts list for the individual coil on box set up.
Bob Bailey. All coil and TR6 box wire terminals and connectors
Amazon 6 Coils GM 12611424
Jegs. 1 plug wire boot kit Taylor 46067
McMaster-Carr. 6 1/2"OD, 1/2" Length, 1/4" screw size unthreaded spacer 93013A330
6 1/2"OD, 7/8" Lenght, 1/4" screw size unthreaded spacer 93013A973
6 Socket Headed Cap Screw 1/4"-20 Thread, 2 3/4" Length 91274A200
What I did was drilled and tapped the lid. Installed the coils and spacers, short spacer on the bottom and long spacer between the upper and lower coil. Placed nuts on the bolts where they protrude through the lid, to lock in place. This was done because the lid is not very thick and I doubt the threads would hold.