I am fitting an oil catch tank to my Ford DOHC 8v.
should I remove the spring, plunger and wirey gauze from the PCV breather.

Cheers

yes otherwise it will not breathe
(its the vacuum from your carb that opens the valve thingy)
On my Pinto I found an adapter in my junkbox that was threaded internally and externally
Luckily it screwed into the seperator opening on the block and the hose screwed into the other end and just junked the valve bit
(it may have been a threaded plumbing fitting? )
Not found a photo of it, but hopefully you get the idea, not that its critical as its not high pressure or volume coming from there hopefully!
so just a good ish fit so it doesn't fall out and spew oil on tight corners

Regards
Rob