Hi Martbass,
unfortunately you can't use much of any of the original equipment, just the spring,the brake servo pipe work and vacuum advance pipe, (no retard on Dells).
The rest you can either buy as a kit like i did from from here. Really helpful guys who will send you the right kit if you let them know you are putting them on a T25 and will need the shortened manifolds.
http://www.dellorto.co.uk/merchandise/p ... ctionID=48" onclick="window.open(this.href);return false;
or speak to Jim at Stateside who sometimes has them in and will put you a set together, otherwise keep your eyes on ebay, VZI etc for a decent set of carbs either drla 36 or 40's will do, but you would be wise getting these sent away for refurb unless you are confident to tackle them yourself, and then buy all the bits you will need to put them together.
There are a few people on here who can help you if you go down this route.
Oh you will need to either put a boss into your inlet manifold for your brake servo, or if you have a word with Jim he can supply you with the correct manifolds and put you a boss in.
You will need to get it on a rolling road once you have it all in to get it jetted up and tuned in to your van. Trust me it makes a massive difference. I drove away with the biggest grin on my face
Hope this helps mate, if i've missed anything i'm sure somebody else will be along to add to this.