69' 1750 GTV Brake Diagnosis

[Eileen Vopelak <stryline@domain.elided>]

I own a 69 1750 with dual brake bosters.  My problem is the brake pedal
seems to need more and more pressure to stop.  The pedal is not going to
floor, as if there is air in the lines, but is just very hard at the end
of the stroke.  I have rebleed the lines, checked for leaks, adjusted
the brake pedal, and am now wondering if the problem is somewhere in the
boosters.  Any advice on diagnosing this problem.  Thanks Dave 69 GTV
v1750

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