My V12 jag has a chev flywheel and a GM Getrag 5 Speed gearbox. The chev flywheel has a smaller outside diameter than the jag flywheel but the same friction diameter - the chev flywheel was 1/10 the price of the jag flywheel bit does not mesh with the jag starter - I bolted a jag flex plate to the crank on the engine side of the chev flywheel - works a treat and is far from a bodge.
In my case no - the flywheel and the flex plate bolts to the crankshaft flange as they would as individual items in manual and auto cars. The flex plate is sandwiched between the flywheel and crankshaft flange - all the flex plate does is mesh with the starter motor and turn the engine - it has nothing to do with the clutch function.