No it won't work.

 

Because of the mount or the tank?

 

Rear is different for sure. Look at Rush seat how it angles up for the frame brace that follows its shape.

 

I wonder if I could just make a different brace?

 

not sure where you live but you could have the seat re done to you specs. and even color options.

 

Wouldn't a seat intended for a Pro-Ride Assault or RMK work???

 

Yup

Linky:
http://www.hardcoresledder.com/forums/552-indy-pro-ride-chassis/1449850-indy-seat-options.html

 

Got one off a switchback that said would work

 

I have the same seat as AK Pro X (the black/white and red one) on my 2013 indy. It is part number 2684894, and the price is currently 155 from Babbitts online. This is from a 2012 Pro RMK, and there are other colors listed as well. There will be a bit of space - about a 1/2 inch - between your mounting bracket and the seat. I took the bracket off the sled and used 2-3 washers between the bracket and tunnel and another 2-3 between the seat and bracket to compensate for this gap. I think others here have just pushed the seat down and bolted it up.