Bolt in replacement sports seat

[TDoherty]

I'm hoping someone can help me out with advice on a new sports seat (type/model etc) for my 1973 240Z. 

I'm planning the odd track day and want something that provides better support than my standard driver seat, supports the use of a clip in harness (I have a half cage) and can bolt straight in/onto the standard mounts. Fixed (with the ability to fix at my desired point) or on runners. 

Like the wheels and tyres, I will be removing the seat after the event until its next needed so I'm looking for something that simply bolts straight in. I'm not looking for a huge winged wonder, just a nice solid supportive sports seat (with harness holes) that doesn't require me to re centre myself in to the seat between each corner. 

Many thanks for your feedback! 

[Millerman]

From what ive been reading there are a few factory seats that require little to no modification to fit in. Other option would be to get an aftermarket seat say a velo or a bride and then make the rails bolt to factory mounts by either modifying the aftermarket rails or merging them to the factory rails somehow