I would advise replacing the pinblock if the pins are loose and the
block has pulled from the back.  It's not an easy job, but it's the
correct way to solve your problem.

Do not drill any holes in the plate.  Remove all strings and pins,
carefully saving the bass strings for duplication.  Make a paper
tracing of the old holes in the original pin block.  These holes
would include the pressure bar holes as well as the plate screw holes.
3M company makes a spray adhesive you can use that holds the paper in
place while you make all your marks on it.  This piece of paper is then
carefully removed.

Remove the pinblock and all glue that remains.  You need good glue-free
wood to glue the new pinblock in place.  I would clean the area and
carefully fit a new block into place.  Do not glue it at this time.
Drill the pilot holes for the plate bolts in the new block.

You can now glue your paper pattern to the new block, aligning the
plate holes with the paper pattern plate holes.  You can drill the
pressure bar screw holes.  Fasten the plate to the piano but still do
not glue the block in place.  You just need to fasten the plate and
pinblock in the piano so that every thing can be checked for alignment.

Put your wooden bushings into the plate.  Now you can mark the new
pinblock for the tuning pin holes that have not been drilled yet.
I usually use a letter "I" drill bit to mark the location of the new
pinblock holes.

Take the pinblock out of the piano with the little dimples you have
made so that you can drill the new pin block tuning pin holes with
a letter "I" parabolic twist drill bit.  I use a drill press with
a table that has a 7-degree angle for tuning pin holes.  After the
holes are drilled run a number 2 "O" reamer from a piano supply house
in the tuning pin holes to ensure that the walls of the tuning pin hole
are straight.

Dry fit the pinblock to the piano with the plate so that you can be
sure all your holes are in the right place.   I use an epoxy glue that
can be removed with heat to glue the pinblock into the piano.  The
epoxy can span a gap up to 1/8 inch and hold the wood like steel.
Elmer's glues or yellow wood glues will let a pinblock "slide" for
years to come.  Since we use an epoxy that can span gaps, the fitting
of the pinblock is not as critical as if you were using hot glue.

As the epoxy is drying I screw the plate and pinblock in place with
a sheet of newspaper between the plate and the pinblock, in case any
glue squeezes out.  I then take the plate out of the piano or lift
it just enough to clean the newspaper off the new block.  I redo the
serial number in the pinblock if that is where it was located.  I am
lucky enough to have many sets of steel stamps for the serial numbers,
so we can match just about any old style numbering.

With a piano that has a bowed plate and that has short plate screws,
I would suggest clamping the plate with many clamps as the epoxy cures.
I would also put in longer screws to hit some solid wood on the
backside of the pinblock.  With the epoxy we use you do not have to
have a tight fit, and if you clamp it the glue squeezes out, which is
not good.  You need a little space for the glue.

This is a technique and now the rest of you can blast it politely.

Don Teach