Are you in need of the entire assembly? If I needed the entire assembly I would use a newer WPC assembly. You would be correct in that the upper and lower right assemblies are the same. Secondly C-9953-L is the left assembly. Where the manual notes the 2 unique parts, these are the only parts that differ from the right assembly.

That depends on weather you are going to replace the existing coils or not. HS coils are series wound and WPC coils are parallel wound.

GRUMPY is 100% correct on the coils if you choose to go with newer style ones.

You also would have to swap out the EOS switches as WPC assemblies use low voltage switches that close when you flip, and older (Sys 11) machines have high voltage switches that open when you flip. High Speed also has lane-change switches on the lower EOS flipper switch stack that would need to be transplanted if you want to keep the engine revving sound when the ball is in the shooter lane. I don't believe think there's one on the upper flipper as there is really no need for it, but I cant recall.

The coil stops will also be different, positioning the flippers slightly different at the end of travel. They can be changed of course. For the upper flipper this won't be a concern.

It sounds like alot but it's pretty easy to use a WPC assembly in any game for the most part; The real question is why do you want a whole flipper assembly? You should be able to upgrade any worn parts easily without needing a whole flipper mech and the headache that comes with that.

It's worth it to replace the old mechs just to get rid of the crappy compression springs.

You can move the old coils to the new WPC mechs if you want to.

Step by step:

https://pinside.com/pinball/forum/topic/vids-guide-to-upgradingrebuilding-flippers

1st. Are you going to upgrade?
2nd. Are you going to reuse your old coils?
3rd. If you get new coils are you staying with stock or upgrading to parallel?
What you need will depend on how you anwser these questions.

Order 1 left and 2 rights with the correct parallel coils, all coils need to be the same on HS.
The EOS switch that comes with is not correct so order 3 of #03-7811 and replace when installing.
The coil stops are not correct for HS so order 3 #A-10280 coil stops from marco's. Couldn't find the right ones at PBL.
Since you are upgrading to parallel coils you will also need 3 of 2.2uf 250v Axial capacitors from PBL.

I myself tend to keep things the way they were. They gave you a certain feel for each brand and system. I still have linear mechs in my older Bally's because I grew up with that feel. Yes they may be prone to more problems, but I'm not tring to make a living off of them. Now this is me, not you. Its your game and you should do what you think is right and nobody can tell you how you feel it should play. I hope I don't stir anyones pot.

Never change the flipper strength.

Just use the coils listed in the manual, or the equivalent parallel coil.

Are you saying that the lane change switches are missing on the bottom flippers. Also there isn't one on the top flipper.

No problems with that, they should move over to the new flipper base using the old screws. Read Vids guide on rebuilding flippers, lots of info and great pics.

I just changed mine over last weekend and had the same issue (wires a bit too short) when I oriented the lugs away from the stop. You should be able to get enough slack by snipping one or more wire ties. You may have to reroute some wires (and then add wire ties to tidy things back up).

Oval the holes of the coil stops so that the bottom moves closer to the coil. Then replace that switch and use your old lane change and a new high current EOS switch. Temporary install a bat in the bushing and put crank on, so you can adjust both switches easy before installing on the playfield. Then solder in the cap and EOS wires. Then your ready to mount to the P/F and add the last wires.