The best manifold/carb setup for a Series V, if you are more interested in reliability than being "concourse correct" is a Weber DGV carb with a Series IV Alpine manifold. It is an easy swap and will bolt right up to your 1725 cc Series V engine.
Most of us that have made the swap sourced a Series IV Alpine for the manifold. Sunbeam Specialties, one of the best vendors for us Alpine owners, has a reproduction manifold that will bolt on and can be used with a Weber DGV carb. I am not aware of any other non-Rootes marques that will have a manifold that will work with the Sunbeam 1725 cc engine.
I have 2 Sunbeam Alpines. I use the Weber carb setup on both of them. The Weber DGV is very reliable and once jetted correctly, can be used for many years with no alterations.
from sunny South Dakota,
67 Series V 5 speed
66 Tiger Mark IA
65 Series IV automatic
64 Series IV V8