Use the old flex plate to be safe. That's what has the holes cut out to create pulses in the crankshaft position sensor. The position and number of holes changed between some years. Your old flex plate has the timing that the Engine Computer expects to see.
Remove the crankshaft position sensor before you separate the engine and transmission so it doesn't get damaged. It's in the bell housing right behind the right cylinder head. You will need a thick paper spacer when you reinstall it to set the critical air gap. Original ones used that paper spacer that you can get from the dealer's parts department. It slides off when you start the engine for the first time and is done doing its thing. Some aftermarket replacement spacers use a thin plastic rib molded onto the end instead. You are to cut the remaining rib off, then use a paper spacer when you reinstall that type.