-=> Quoting Ralph Hawkins to All <=-
 RH> @MSGID: 1:123/316@fidonet.org 34f13668
 RH> Hello All!
 RH> Forgive me for posting this request again, but my link to Fido has
 RH> been down and I would have missed any replies.  Have a friend who needs
 RH> a #1521  6v 6 amp bulb.  Any help is appreciated.
 RH> Ralph
My first try would be a Volkswagen shop or an "old car parts" store that 
specializes in older parts.
My next suggestion is a bit "left field" but will work according to Ohm's
law.  If you can find a 12 volt bulb that will fit in the socket (I have no
idea what a #1521 bulb looks like) and then wire an identical bulb in
parallel to the brake light it will cut the resistance in half and it should
light up to full brightness at only six volts. 
Also a bulb that runs at 6 volts at 6 amps is using 36 watts
(wattage=volts x amps), If this helps you any in finding one.
Here is some help with the wiring (that is if you need it):
                                     splice
From fuse    >--------------------------o------------@  <-- brake light
                                        |            
                                        |           
                                        @  <-- identical light in paralell
                                        |
                                        |    Use wire ties, etc. to position
       Ground this end to frame    -->  /    light so that it cannot touch
                                             any other wires or bang against
                                             anything.
Good luck :)   
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