Firstly, many congratulations on the new arrival. Don't forget - we want pics when they arrrive!
It's sensible to use the feed your dog is used to in the kennels, at least initially. They will have plenty of adjusting to do once they get home and continuity of diet is one less thing to worry about, and will hopefully keep things working smoothly. Even with the same food, it's quite normal for tums to be a bit sensitive for the first few days, often as a result of the stress of moving.
Once you are all settled, you don't have to use hound-specific food, any good quality dry food will be fine. We used James Wellbeloved but you'll see many people having good results with Arden Grange, Burns etc. As with any dog, avoid any food that is stuffed with dodgy colours, flavours and junk. Earlier this year, we moved on to a BARF/raw style diet so no longer feed kibble, mainly because one of the greys has a very sensitive tum and this is working very well. However, feeding a good quality dry food is great and works well for many people.
As well as the kibble, it's a good idea to occasionally give variations (helps vary diet) such as sardines, pilchards (good for coat), the odd egg, leftover bits of pasta, rice, cooked veggies etc.
Many greys coming off the track have poor quality teeth as they've not had much hard/crunchy food - if yours has already had a dental, give regular bones etc to help keep tartar off teeth. It can also be a good idea to get your grey used to tooth brushing.
Good luck! Just one warning - they are completely addictive....