Question re: BB spindle length

[Gothard]

Now that I am assemblig The Hors Cat (Johnny cash), I realise that I am missing a BB. I was all ready to go find one, when I remembered something about spindle length in relation to frame seat tube diameter.

Is there any truth behind that, or am I ok if I get a 111mm BB for the Record triple on the Hors, which has a 34.9mm seat tube?

[Gothard]

Anyone?

[R2D2]

I personally have never heard anything about spindle length and seat tube diameter.
I would think you just get the right bottom bracket for the BB shell
(Italian or English), although I think Serotta's are English. Then get the right spindle length for the crankset.
Now of course the clamp on derailleur size depends on the seat tube.