Urgent help!

Will the seats the seats from an 89 Civic Si fit into a 91 Civic STD? and if not what modifications are needed?

I dunno about 89, but I have a 91 dx and my Si seats do not fit. the rails are different, one of them bolts up just fine, the otherhas one hole off by about 2" and also there is a raised portion under the seat that isnt on the SI, so the rail has a gap between the seat and itself, about 1 1/2"..again, 89 may be a little different, if you have the Si Rails then they should go in.