here are some pics or the stock rails and the floor mounts

apparently the early 120ys have a different floor pan, i got told the later 120y's have a bigger tunnel?? but im not sure. the mount on the tunnel side is about 40mm higher.

You can add the information to the wiki. Anyone can add to it.

I put general information in there, applicable to other cars. You can see pictures of my B310 seat rails there, hopefully the ideas will help someone.

Early B210s I thought had even mounts like B110 then later B210s were different -- or so I thought.

ddgonzal the wiki doesnt show anything on putting them into 120y's, i've already looked there. I dont really want to cut the floor either. I might just have to extend one braket to raise it up so that its level to the other.

mine has had the high side on the floor cut down and rewelded at the same level as the other side. perfect height.

i install a wrx seat. do u really want to know lol it wasnt the funest thing to do as i wanted to retain seat rails the biggest problem is getting it to sit low as just bolting it on top with spacer on outside rail is wayyy to high.
i had to cut to inner rail down(pretty much remove completly on passager side) so that it was level with the outside one not sure about manual tunnels but mine was an auto tunnel , also note the passager side is much harder due to the big extra muffler hump.to over come that i had to bash the corner of tunnel and floor out a bit i will be able to get u photos by the end of next week if u really want?

I know exactly what you mean bud. My way around this when it comes to that part of my build might be to mount the seats to the rollcage (I've seen an article about it in the cams mag and apparently it's considered a good idea although not mandatory atm)

pics and diagrams here: wiki - Seats

I just bought a sparco replica seat and i want to put it into my 76 120y (which is the late model). If anyone has put a seat in a late model 120y they will know what im about to ask, the rail closest to the tunnel is aprox 40mm higher the the rail closest to the door, and the stock seat has a matching indent in it to match it so it sits flat. does that make sense?

How have you put one in your 120y? pics would be a massive bonus.