Split the old one off using a sharp cold chisel in a gap between two teeth and big hammer. Clean up the surface. Cool flywheel in freezer, and place flat on bench. Heat the new ring gear until good and hot - when expanded enough it will drop into place.It will shrink as it cools and grip the flywheel really tightly.
Repair starter motor is best cost option. My local auto electric shop did mine for £30.
For flywheel, Ford Capri's are my bussines. There are two type's of flywheel with different clutch and pressureplates which you can not mix and match.
Early and late. Ford changed Early seventies to late style flywheel while Relaint on his Scimitars and others went into the eighties using the early ones. Essex V6 is used in many brands like TVR & Marcos also. Also widely used in fire brigate waterpumps and so on
I don't have one. 3.0 V6 Essex parts are very rare on the continend as its all Cologne V6 here ( 2.0 V6 / 2.3 V6 / 2.6 V6 / 2.8 V6 and conversion 2.9 V6 ).
Ringgear itself is interchangeable on both flywheels.
Interesting, the starter I have is a OEM Ford unit made by Bosch, Part # is 952C-11000-AA.
I tried one of the geared starter units supposedly for a Essex V6 and the engagement with the ring gear was out just enough to chip the tips of the ring gear teeth off and that's why after I had it on for a few months, I had to replace the ring gear.
So if one is to buy a non OEM starter (or I'd think any starter for that matter), be sure to measure the gear lash before final installation. Obviously, the best opportunity is while you still have the trans out of the car.
Not sure of the origins of this EBay posting but this looks like something to consider.