I am looking for projects to publish, if you have something you think belongs here .

Crosby Spica Mods / Crosby "Strads"
Perhaps the most well known mod of the period was the Crosby Mod. Crosby was a "A High End Audio Specialist" located in Hobbs, New Mexico. They were well know for modifying a variety of gear, but perhaps best known for their Quad ESL modifications... (more)

GR Research
Replacement tweeter with matching crossover with significantly upgraded components in a kit. They also offer components to upgrade your existing crossover if you are just trying to replace aging components. There has been much written in the boards about this tweeter swap and the crossover kit and while it may produce a good sounding retrofit, the considered opinion is that the finished product will no longer be a time aligned design.

Basel Audio - Building Classic Speakers
Technical review of the TC50

Tommy Tube - Pimping the Classics (also Spica related links)
Link to Spica Review, Audio Magazine 3/84