I used a pair of gearbox clip pliers to expand the self cancel clip - and gently tapped it down with a pin punch.
Helps to have 2 people.
It may pay to bend that prong on the copper ring so it goes up the hole. The wire may end up to short otherwise.
I believe I read a post from some time ago that stated OEM trim rings had a oval valve stem hole and later remanufactured type had a round hole.
I don't know so I am not attacking just a discussion point.
The coupler rebuild kit I got from Mega Parts had the pin in it.
Don't have one to measure.
Solid pin - tap fit in that hole about 5/16 to 3/8 long.
If it is coming out maybe your steering column is collapsed. The "shoes" of the couple should be way down inside the coupler.
I installed all of them dry. The cork gasket does the job because oil pressure which is in theory nearly equal is on both sides of it.
I think the bolt torque is 45 foot pounds.
I would use the cork in that position to allow the cork to compress and allow the adapter to go tight enough to seal the adapter so you don't get an external oil leak.
Been a while and my memory is not so good - there is also a pipe plug to install in the block - 1/4 NPT I think.
The reason I suggested using the stock bolts is they can only be used with iron heads.
The washers on the ARP allow the soft aluminum head to be protected from the fastener as it tightens.
ARP makes good stuff.
I read if the car was equipped with a factory high performance engine it also got the black grille and tail panel.
My car is a non R/T with a 340 and it is black in both places.
There is a post on the FBBO site you should look at.
Vapor Separator is the title posted by Charger Fan.
The diagram and explanation posted by Vaanth will help you for sure.
I wouldn't worry about the liquid fuel return. The car never had it originally and fuel vapor lock does not seem to be one of your issues.
I would concentrate on the fuel tank venting side of things.