Catalyzes the radical-mediated synthesis of 5-amino-5-(4-hydroxybenzyl)-6-(D-ribitylimino)-5,6-dihydrouracil from 5-amino-6-(D-ribitylamino)uracil and L-tyrosine. 5-amino-6-(D-ribitylamino)uracil + L-tyrosine + S-adenosyl-L-methionine = 2-iminoacetate + 5'-deoxyadenosine + 5-amino-5-(4-hydroxybenzyl)-6-(D-ribitylimino)-5,6-dihydrouracil + H(+) + L-methionine Binds 1 [4Fe-4S] cluster. The cluster is coordinated with 3 cysteines and an exchangeable S-adenosyl-L-methionine. Cofactor biosynthesis; coenzyme F0 biosynthesis. Consists of two subunits, CofG and CofH. Belongs to the radical SAM superfamily. CofH family.