As Doug said, there are several Weber intake manifolds depending on which heads you intend to use and some will not interchange. Some are cast-lettered 'DeTomaso' and some are not. Plus, original Weber 48 IDA carbs have been out of production from Weber-Italy since the mid- '90s when the company was sold. They were last reproduced in Spain later- with visible differences- and today I have no idea where castings are made. Some weber-lookalikes are much larger than 48mm, used on dune buggies. There are also at least three different types of Heim-jointed linkage. There are EFI throttle bodies from TWM that look similar to Weber carbs, and might be a solution for some.
Be prepared for even NOS Weber carbs that have never been on an engine to leak gas when first run, due to the seals and gaskets drying up over 50-60 years of sitting on a shelf. They may need rebuilding right out of the box. A sorted, running setup is a better choice than all-NOS. There are a few places that stock jets, venturis and floats for tuning these carbs, which are complex to get running well. There are five jets and two air-bleeds for each cylinder and you have 8 cylinders. The usual is to either have good power and poor mileage, or tolerable mileage and low power. Don't want to discourage you, but a set of Weber carbs may need considerable expert dyno tuning. Good luck.