Maybe we can work on this together as a project. re-manufacturing in brass would be a expensive way to do it . If it's for looks only, and not a operating filter, I would machine the filter body out of aluminium, once painted, nobody will notice any difference. If you can provide me with good drawings or good detailed photos of the original filter , I will make the filters , and make two extras for you . You could make a mold from an original lid and cast the lids with a modern epoxy and finish off in a lathe or whatever
MW Bedfords are scarce over here, I've only ever seen three myself in 40 years , two rusted out relics beyond help and one complete nice original truck , but I know of at least 5 others . Nobody has restored one over here.