When the Avanti was being designed, an upgraded brake system was part of
the plan.  Stude turned to Bendix for the brake system, probably because
Bendix provided many of Stude's brake system parts (they also obtained some
from Lockheed).  I am guessing that due to a short lead time Bendix went
with a combination of off-the-shelf components and some rework of an
earlier design.  

The rears were a slight rework of their earlier non-servo design with cam
adjustment, although the drums and shoes were unique to the Stude disc
brake application.  Why drums instead of discs on the rear - probably
because an effective emergency brake was easier to incorporate on rear
drums.  The early Dunlop emergency brake with the two 'fingers' was not
very effective (and the pads for the emergency brake are virtually
impossible to find today). 

For the fronts they chose disc brakes likely because of their proven
effectiveness by Dunlop and Girling.  Bendix could have designed a disc
system themselves, or had Lockheed or Budd do it.  Lockheed had designed
disc systems for aircraft for years, and Budd had designed disc brake
systems for their railroad passenger cars since before WWII; but as I say,
I doubt there was time for this. 

So Bendix chose to llicense the 'off-the shelf' Dunlop style calipe, altho
their disc design was unique to Stude.  Since Bendix was making a large
quantity of cylinders from Dunlop for OEM purposes they had the Bendix logo
cast into them, altho the first version had no name cast and a Bendix label
was used.  Later version had 'Dunlop license' also cast onto them.  For
originality judging any of those styles would be correct.  Later service
replacements were bought by SASCO direct and had the Dunlop name cast onto
the cylinders.

Bendix chose the 2-1/8" cylinders then currently used in front on the XK-E.
 XK-E rears used the same cylinder, but with a 1-3/4" bore.  Jaguar was
probably Dunlops biggest customer up to that point as they used the Dunlop
calipers with the XK-150 and several sedan models.  After about '68 (would
that be starting with the Series II?) the XKE no longer used the Dunlops.
Other manufacturer's used the Dunlops to some extent.  They can be found on
MGA Twin Cams, Mercedes 300, Ferrari 250 & others, the Aston DB4, and
indeed even on some Datsun's.  Note these date to the early 60's also.   

Some applications used a larger cylinder on the front brakes (2-3/8" bore
AFAIR) and these applications used the larger NAPA S703 pad.  These
cylinders and pads were used by the Mark IX Jaguar, the Aston DB4, and the
Ferraris with Dunlop brakes.  In all cases where Dunlop discs were used in
the rear, the NAPA  S702 pad was used, but the cylinder bore could vary
between 1-1/2 and 1-3/4" depending on the car.

So to summarize, yes, Jaguar Series 1 XKE, and other, pads will work, and
Jaguar XKE Series 1 front wheel cylinders are a 'bolt-in'.  But do not use
Jaguar XKE rear wheel cylinders.  Nor will Jaguar XKE rear wheel calipers
work. And in fact I am not sure that Jaguar XKE Series 1 front calipers are
a 'bolt-in', but it has been too long since I have worked on a Series 1.
Nor do I think that XK150 front calipers are a bolt-in.  I seem to recall
that there was something different about the two mounting bolts, but it has
been even longer since I have worked on an XK150.  Anyway, one does not
normally need a caliper unless you snap off one of the cylinder mounting
bolts....................

In retrospect, considering the weight of the Stude's, it might have made
more sense to use the S703 pad model, but I suspect there was a cost issue
too.
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