While searching for midibox SID stuff I stumbled upon Subatomicglue's super-extensive build log. He has info on almost every aspect of making a SID synth. It follows the panel design of the original Midibox SID made by T.Klose and it is packaged inside a Commodore 64.
He has used a custom made panel (Made by Schaeffer)
and he is quite good with the soldering gun :)
More of it on his work log