I have a pile of 13B parts that are looking for a good home.  As I
 recall there are enough to build about 1 1/2 complete engines, but
 everything is disassembled and in a pile so I can't really confirm.  I
 *think* they are in serviceable condition, but no guarantees, I'm a
 rotary newbie.  If anyone wants to stop by 02C (just South of Milwaukee
 WI on the sectional) and pick up them up, for free, please contact me
 offlist (bob@wheelerexpress.com).  I'd prefer not to ship, but that's
 negotiable I suppose.  I will hold everything until OSH if any takers
 are driving up 94 on their way to the airshow, after that it's the
 scrapyard.

 Also, I'm in need of a carbon fiber spinner and backing plate as well.
 About 13" diameter, long and pointy, SAE 2 hub (I think, have to
 confirm).  If there are any left over from that earlier conversation
 please contact me.

 Thanks,
 Bob

 Bob,

 I would like your parts!  I can even pay you something!  I will be
 attending
 the AirVenture at OshKosh and will have a rental car.  Since I am
 flying in,
 I will just have to ship them to myself back in Texas, which I will be
 happy
 to do.  I would like these parts just to experiment with how to best
 reduce
 the frontal dimensions of the engine, and as such, do not need a
 working en-
 gine.  I will also reply to your other listed email address.  Thanks.

 Gene Kahn

Hi Gene;
Take a look at the Powersport installations - they are still way ahead
in this regard.
Pport with throttle plates in the housings, tight bends on the intake
and exhaust.
http://www.protonet.org/doc/index.htm#powersport
Paul has better pics of a tighter bend radius.

For a stock 13B, replace or cut down the oil filler neck and chop down
the waterpump.
Relocate the alternator to the side (Pineappleracing.com) or go
permanent magnet on the flexplate.
RacingBeat/Mazdatrix sell oil filter relocation plates.
With more radical mods you could remove the rear iron filter stand
entirely and drill/tap
new passages, plug old passages and improve oil flow in the process.
You can get a few more inches on the bottom by removing the oil pan.
Replace the pre-3rd gen CAS with 3rd gen/Rx8 CAS pickups.

If you hang around rx7club.com you may get most of an engine core for
(near) free if you haul it away.
Bits of 2-3 cores will probably get you a complete core in spec for a
rebuild.
The hardest part is getting decent rotor housings and side seals.
The best cores are ones that smoked due to leaking oil seals, possibly
ones that blew a water seal
(as long as it didn't sit too long to rust)
Cheers
Cary