The use of a 500k volume and 250k tone pot has me scratching my
head. One uses a higher value volume pot to hang onto high end.
Using a lower value tone pot seems to me to risk bleeding the high
end one is striving to retain, not unless you plan on using a fairly low
value tone cap (e.g., .01uf) where you won't notice the minimal
treble loss. You may also want to consider trying the open-circuit
pot mod, where the last few degrees of rotation of the tone pot
result in no continuity, effectively removing the tone pot from circuit.
One does this by removing the back cover of the pot and
judiciously applying some type of insultating laquer over the last
couple of millimeters of conductive material, in a thin enough layer
that the wiper slides over it.
 
As for cap type, some of the best instruments ever made use
crappy ceramic caps. I wouldn't put too much thought into the type
of cap.

I tend to like 250k for a setup like yours.
 
Maybe a 250 vol and a 500k tone whats cool about a tele is that
you can run two wires out under the plate and tack solder different
type/value caps until you find what you like.
 
On the vol you can try a cap from the hot to the wiper.
 
Steve A. has some stuff at his site.

The pots I purchased were the recommendation of something I read sometime ago. I have no idea now what the reasoning was. I have noticed what you are saying about the last few degrees of a pots highs.
 
Gus
I like your idea on running the wires outside and trying different
caps.
I'm going to take a look at Steve's site and see what I can find. I
talked with Lew Collins (Bruce's brother) a while back about the
Lindy Fralin's but I can't find his email address now?
 
Thanks again
RJ

     I like loud raunchy sounds so I usually use 500k volume pots
with my single coil pickups. Even when set to 10 the 250k pots will
bleed more of the signal (and highs) to ground. But sometimes there
is just a little too much high end to begin with so the 250k pots can
mellow things out nicely.
 
    You can convert the 500k pot to a 250k pot by adding a 240k
or 270k resistor from the wiper to ground. It will affect the taper a
bit  I call it a "super audio" taper since it exaggerates the normal
audio taper a bit. When set to 10, your amp and pickups will "see"
a ~250k pot.
 
    Pots modified by resistors work better in guitars than amps
because the added resistor can change the impedance seen by the
preceeding stage  in a guitar the "preceeding stage" would be the
pickup... Just the same it can be interesting to experiment with them
in guitar amps since sometimes the varying load on the previous
stage can be desirable.
 
    See how you like the Lindy Fralin pickups with the 500k pot  
if you need to tone it down a bit you can always add the 240k or
270k resistor from the wiper to ground. Will you be using a 4-way
tele switch from Fender? The added linkage adds a lot of versatility
to a tele. I also used a push-pull pot to put the pickups out of
phase, and used the modified TBX circuit for the tone control on
my 1969 Thinline. (Is your tele body chambered?)
 
--Good luck!
 
Steve Ahola
 
P.S. For tone caps a decent .022uF poly cap works pretty good.
For a bright cap between the two ungrounded terminals of your
volume pot you might try something like 250pF, or you might try a
larger cap in series with a resistor. The RICHIE SAMBORA
STRATOCASTER uses a 10k resistor in series with a .01uF cap
but maybe someone else here has some better "recipes" for RC
bright networks.

    Two suggestions: Lindy Fralin pickups and Lindy Fralin pickups!
 
    Actually the 2nd suggestion would be to get a Fender Custom
Shop 4-way tele switch (which adds the neck/bridge series linkage
for a very full yet clear sound).
 
    Like Chris suggests a steel bridge may be an integral part of the
classic tele sound... I assume that he meant the "ashtray" style
bridge with 3 barrels. You might look for the oversized brass
barrels.
 
    BTW did you shield the bridge pickup? Lindy Fralin
recommends that you not shield his pickups with copper foil tape
because you will lose some of the high frequencies...
 
--Good luck!
 
Steve Ahola 
  P-90's can get kinda muddy
sounding but the Fralin SP's have a lot
of definition (if you are looking for the
dirt from a P-90 then you better look
elsewhere). If someone rarely uses his
strat bridge pickup because it is too
damned harsh, the Fralin SP is definitely
worth looking into.
 
Steve Ahola