If you did not get any documentation with your Weber carburetor, go to Ack's FAQ and do a search for
weber. There you will find lots of documentation on the Weber DGxx 32/36.
You only need one vacuum hose to make the weber work with your engine - the vacuum advance for the distributor. When you remove all the hoses from the intake manifoild (the vacuum advance port is on the carburetor itself) you will need to plug all the vacuum ports.
As for the electrics, simply disconnect and seal off each connector to prevent electrical shorts from occuring. Tie the connectors up out of the way so they won't be damaged or cause damage.
If you want to play it safe, find an intake manifold and permanently plug all the vacuum ports. While you are at it, cut the center section out of the air/fuel intake port and smooth down the edges to get better airflow from the carburetor to the intake plenum. Use this for the Weber and the old intake for when you want to switch back to the Hitachi carb for emissions tests.
Finally, before you totally give up on the Hitachi, check out these pages at Ack's FAQ:
http://www.acksfaq.com/Samvacuumlines.phpand
http://www.zuwharrie.com/component/option,com_smf/Itemid,40/topic,21551 (unfortuantely the pics are missing at the top but the information is good)
Maybe you can ge the hitachi running well enough for it to pass emissions inspection then remove it for the weber.
Note that there are other alternatives to the weber carb these days - each with it's advantages and disadvantages. try the search engines on the forums and use the search word
carb or
carburetor.