I'd recommend getting a pull type plow and putting a power unit on it.  That way when that dozer dies or you want to upgrade etc you won't have to fool with swapping plumbing/valves etc.  Making brackets for a mounted plow and custom configuring/installing pumps on output shafts on a real old open center dozer costs a lot of time and money and you seem like one that likes to save.  Just my opinion but speaking from personal experience here.