Dave, Yes it would be good to have some tangible and dependable informations instead of some old (2nd party) stories and recollections.
Don't want to start arguments but as a Fairchild collector I'm strongly interested to know if they produced amplifier kits or not, but so far I was unable to find any reliable informations to confirm they did. I'm still searching but statements like "I KNOW that"... or '" A friend's friend built one many years ago..." have very little weight to me. OK, call me incredulous. But when you intend to do some historical research work you should be, and cross-check your sources.
As far as the 412ED Retrofit KIT is concerned, it consisted of a fully assembled electronic drive chassis and some accessory parts (knob, wires, hardware, cover plate ?...) needed to mount it in a 412-1 basic turntable. You might do this work yourself (and save 7$) or leave it to your dealer. The (quite complex) electronic drive circuit was never offered in kit form (the price differential would have been MUCH greater). But you may still call it a "KIT" if you are so inclined, after all that's how Fairchild named it. There was also a 440 turntable (440-2K) in kit form, that I'm sure of because I have the original assembly manual and it can also be found advertised in some old mags.
All this to confirm that Fairchild DID actually offered some Hi-Fi kits but these can be traced and documentation/ads can easily be found. And then why nothing about their amp (kits) ?
I think it's quite possible that at some point unbuilt Fairchild amps appeared on the market in kit form but it's very unlikely they were produced by Fairchild. Most likely someone bought the remaining parts stock and made some (semi) kits of them. The fact that they were unlabelled (unbranded) and without S/N tend to support this idea. Most other kit makers (Heathkit, Eico...) had a S/N printed on the chassis or on a sticker. The Fairchild packing box labelled "Kit" would be very interesting to see.
And strangely enough nobody has ever seen a Fairchild Kit amp assembly manual which was of course essential to build the unit.
Again, I have only seen a few (N.O.S) 255 amp chassis offered for sale (unlabelled,with some factory mounted parts and harware) and transformers sets. But no boxes, manual, passive parts... just not what I would call a kit. And absolutely NOTHING can be found about 260's and 275's in kit form...