I dont know any sites but i've done a bit of a custom dash in my corona mk2.
I cut a square hole out where the am radio was (it was in line with the gauges all ready in there) got a piece of jarah cut it to size drilled two holes with me hole saw in went the oil & water temp gauges.I used would cause my steering wheel is wooden and i made a custom arm rest out of wood, My gauges in the middle (speedo fuel, temp) are in a 3 holes (one was a clock other was speedo the last one was fuel/temp) your celica may be the same depending on what age.
anyway i ripped the clock out put a tacho with a shift light built in into the hole where my clock was, hey presto custom dash.
If your not in to the wood look use chrome sheet metal(flat of course) and get drillin.
just make sure u get some one electrically minded to wire the shh up.