Overview: A lot of folks like the FT-243 mount, it lends authenticity to your older equipment.. You can easily convert the HC-6 pins to larger pins but still the HC-6 just doesn't look right when mounted in that older military or amateur transmitter and receiver.
PLEASE NOTE: There are several processes presented on these pages, The first method shown on this page for remounting the HC-6 crystal blanks does not work reliably and often results in a fractured crystal but other methods that are shown on pages 2 and 3 are easier to duplicate and they work.
You choose, which holder do you like the best. 
Unsolder the HC-6
Expose the crystal
Carefully
unsolder the crystal from the wire mounts. Good luck.
Disassemble the FT-243 holder.
Save the FT-243 crystal that you removed for future "grinding" projects.
Clean
the HC-6 crystal blank including removing the microscopic traces of solder
and place in the in the FT-243 holder and reassemble.
Test
the crystal. A grid dip meter is a fine instrument for crystal testing,
you can vary the circuit characteristics for the crystal being tested by
simply varying the frequency dial of the meter. 
During
the removal of the wire leads from the HC-6 crystal blank I often wound
up with a fractured crystal.
First Process Conclusion:
It
don't work.
Why doesn't this work? Well each time I was probably
unsuccessful in properly cleaning the crystal of minute residue and the
HC-6 crystal blank has a metal substrate that the pins solder to. The
FT-243 holder does not like the metal substrate surface so it doesn't
oscillate... but the really big crisis was that in the process I sent
several HC-6 crystal blanks to never never land.***
I am sure that the leads can be removed from the HC-6
blanks and that the "transplant" process can be accomplished
but still you have the danger of fracturing the crystal blanks and wasting
a lot
of time and crystals . . . So I put this first
method in the "too hard to do box"
*** Never , never land, means
South, the same
place those 807's,1625's, 829's go when they fade away.
The HC-6 crystal design looks very fragile but is reliable.
Anyway enough of this falderah go to page
two for a better method of using the HC-6 blank in a
FT-243 holder.
PAGE 2