Does anyone know if it is possible to put RCF/GSF seats into an IS? If so, does anyone know where I can get a set?

 

Ebay is your best bet. They will be really expensive if you ever see them there. I have seen 2014 Fsport seats for $2000.

I'm not sure if the bolt pattern is the same for the brackets. It may be. I would have to see them both.

 

the seat brackets (Bride brackets) are a bit different from the 3rd get IS to the RCF. you'll only be able to fit three out of the four bolts on both driver and passenger seats. this is EXTREMELY unsafe. 2IS brackets are identical to 3IS brackets though. so ISF seats would be your best bet. either that or you can make your own custom brackets. You'll have to modify to stock RCF bracket though cause its part of the stock seat. good luck