I have bought an engine and auto trans from a late Type 3 wagon to fit into a 63 Split window Bus.I would like to use the twin carbies on it,but found the carbs to have a strange spring and rubber bung on the throttle shaft plates.I have never seen these before,so am guessing it has something to do with the auto trans.Does any body have any clues.I guess I can remove them and plug the hole.

I assume your talking about the part in this picture just above item number 51/52?
https://www.thesamba.com/vw/gallery/pix/638334.jpg 
These carbs were on all type 3, type 4 and kombi's that had dual solex (though they did change specs for each application). Yes this was an extra valve fitted to auto's, it's for cold starts and helps hesitation in colder climates on auto's when cold that wasn't as noticeable in a manual. The plate holding the valve in is a bimetal spring, so changes force with temperature.
Kombi's had a cover over this (I have a few), but think type 3's were like you show.

I have never found spare parts for them, and most gasket kits don't include seals for them either. Provided cold starts are not an issue for you, they can be sealed up as you said.
Being a QLD'er I have never noticed a change with/without this part.

for a stock motor if they are in good nic these carbs work great. But as with all Solex carbs, they suffer badly with age, make sure you get a GOOD gasket kit, check all mating faces are flat and clean and look particularly for wear in the throttle and choke shafts which give bad air leaks. Also check the fuel inlet tubes are TIGHT an not a potential fuel leak!
Another bad wear area is the linkages (ball and cup) which makes them impossible to synchronise, and really bad ones have a lot of wear in the throttle and choke butterfly

Yes Andy -that's it.Until I strip the carby and check it out,I can't figure what they do.I have some Type3 twins on my Buggy that came from a manual car-and that bit isn't on them.The throttle shafts on these have no wear,but every ball and socket on the linkages are totally buggered.I use those Redline ball and socket arms to convert the linkage over.I machine the hex bar to fit inside 8mm steel fuel pipe,then silver solder them.Can make the linkages any length or shape you want.The OG ball ends are easy to remove-just grind the back off,punch out,then drill out to 5mm to suit the Redline threaded ball.I have a couple of overhaul kits coming from Cip-have never heard of Tooleys-will google them-Thanks for the word.

Yes those bi-metallic valves did "something" on Auto. (only) type 3's, the question as to what they actually were meant to DO was discusssed here before several years ago: thread started between 18/4/07 & 2/3/06, by Joel?

https://forums.aussieveedubbers.com/viewtopic.php?tid=49427&page=1#pid555555 

It seems if they are complete, clean, and cover/seal the holes when cold, they can be left as-is...