I actually did this about 6 months ago and i recently took some pics of it. As some of you know, there is no single A-pillar mount gauge pod available for the WRX. I experimented with the GReddy universal pod and i didnt like it. I probably could have made it work but it didnt fit well......took up most of the A-pillar, too bulky.
I did not want to buy a exhaust temp gauge.....i dont think i will be going past a Stage 2. So i decided to buy the A-pillar mount dual autometer guage pod and cut out one of the pods. I used the bottom pod because the top pod has more depth in it and a large gap would appear on the back of the pod. As for paint, i went to a paint shop and purchased some grey wall paint (closest match i could find) with an "eggshell" finish (appears less glossy). I mounted it with double sided tape and filled the small gap in the back with a thick grey foam tape.
Let me know what you think!