Many thanks for the replies...
@Citoyen du monde...
I just got the Gran Sport one so I'll probably keep it for a bit I'm afraid. It's NOS and lovely, just needs bearings. Have to say, I wish I had a Masi Special it could grace! I've also got a Campagnolo Sport Steel crankset, so if I don't use the headset on the Rotrax, I'll use it with that crank on something later I reckon. Although I may start to get short of funds, so I'll let you be first to know if I need to recoup some money to help finish the bike!
Do you know when the GS Headsets date from? Velobase has it earlier than I would think, seems to be mixed up with the "Serie Strada"- part No.1039. The chap who kindly sold it to me said it didn't appear in his search of catalogues until 1971.
As for leaving out the washer/spacer... easily done on the GS, but can't do it with the TDC headset (S type)
as it uses a toothed washer that fits the toothed upper race.
I had actually been thinking of using Mafac centrepulls. Would this really not be period correct? On the shimming I thought that'd be possible, so I guess altering the forks crown to 26.4 isn't a bad idea.
I woudln't mix and match the two I have as they're both very nice examples of what they are. NOS GS and close NOS TDC. But did think about mixing and matching old headsets, but the trial and error of finding nice condition period bits to play with might get expensive!
Again thanks for the help.