I have a convertible and a set of rears seats from a couple...there is no way on God's green Earth that the bottom section from a coupe will fit in the 'vert, (al least not without the use of a saw-all) it is at least a foot too wide
it may be possible to wedge the back, folding parts of the couple seats in. But I haven't taken it apart to try...I suspect even if they fit mounting them would be a PITA