I’ve added WPC mechs to my games all the way back to firepower. All I’ve had to do is get this setup and make sure the coil and eos is right.

https://www.pinballlife.com/full-flipper-assembly-for-williamsbally-machines-from-021992-to-101998.html

https://pinside.com/pinball/forum/topic/another-funhouse-playfield-swap-3/page/3#post-5619810

You can upgrade the mech to 'fliptronics' style with extension springs, but that won't remove the need for a high voltage eos and the capacitor. Not really feasible to add a fliptronics board

What eos and coil stop would be needed?

You would need the normally closed EOS here. It doesn't mention whether that also includes the capacitor or not..

Coil and coil stop should match the diagram in your manual, same as with the current mech

The coil stop that comes with the mech if you’re replacing everything.

Make sure the eos is normally closed for this game and that the coil is proper per the manual. These are all options on pinball life to make the mech proper for your game.

the only other real difference with the fliptronic style mech is the extension spring. It's pretty easy to convert your existing mechs to use it too.

Now I'm getting confused ... I can just convert the spring and it's now the same? No need to buy the pinball life kit?

No need to buy the kit if you have everything else. The older the game you’re converting, the more parts that will be different and it would make more sense to get the full assembly.

Funhouse is the start of WPC so the mech is almost the same outside of the pawl and spring.

The only difference between early 90s style mechs like funhouse has and the later style is that early use a conical compression spring and the later style uses an extension spring. The extension spring requires extra bits to mount it to, but you already seem to have those in your pic (the plate sticking out of the crank, and the holes on the EOS mounting bracket).

The other differences between the older and newer units are that they use a normally open EOS (without capacitor) and a taller coil stop, but you need the normally closed EOS and capacitor to work with funhouse since it doesn't have a fliptronics board, and you'd want to keep the same coil stop so that the flipper still acts the same as before

It's the factory flipper set up. Do I need the kit ? Will I need a capacitor or can I just transfer over my old one? Thanks to all for the help !

Are you doing funhouse too? If your mech looks like the one pictured by the op above, all you need to do is replace the spring. And yes on capacitor. If the old one works, use it.

Rudy and I thank you !