First would suggest you do a lot of reading, on everything 240 and car related.
First for KA-T (though at this point I would not suggest you do anything), read:
adding-a-turbo-to-a-stock-ka24-noobs-read-t226410.html
Secondly, true coilover springs will be the same size on front and rear, though for a 240 the spring rates will be different. If you only want 1" drop just get lowering springs.