this is like asking how many people you could make if you were to **** around with the genome.
the whole point of custom is that you choose the build.
if i were you i would get 74/75 angles 120mm spacing and stiff steel tubes, tig welded if your builder's good at it.
but at that point, you could just get a professional fit and find a production track bike that fits those specs.
i'm actually considering selling my cross and track bikes and saving up for a custom Ti track bike. there are tons of builders here in seattle. or a steel Winter cycles bike, because I really like eric's style and finish.
I really can't decide right now, but I kind of hate having three bikes and not being happy with any of them because of various things.
and Vix... no one needs a custom frame. no one needs to ride a bike. we chose our own path in life and that's what makes it worth living.