This is the reason a PMA is not for everybody.
Lose of timing marks.
Most people should keep there old system so they can re-install the basics and be able to time ignition systems.
Valve maintenance is easy done without any timing marks.
Ignitions not so.
Other issue with PMA is most if not all have 5mm woodruff keys and crank is 4mm, leading to owners making their own, which can lead to small inaccuracies in timing. Not critical but still possible.
I don't recommend leaving a woodruf key out because if you ever have the rotor come loose at all, it spins and ruins your crank shaft. Key helps to prevent that even if it's the 4mm key in a 5mm rotor.
Others use degree wheels and establish new timing marks, something not for the average DIY guy.
Using a piston stop to find TDC for a degree wheel I found backing off both intake/exhaust valves for the cylinder helps to prevent bent valves due to valve contacting the piston stop.
Best advice, get a knowledgeable mechanic to do the work, use old system for this purpose or get educated and acquire the tools, degree wheel/piston stop, and do it yourself.
My 2 cents.