I would have thought so, if its a ph3 then you should only need the dials, jsut done that to my ph2, all i need to do was swap over dials, water temp and revs worked...and my previous dials didnt have either on.
Someone had this done wiht ph2 dials to ph3 and paid about £70 to have em converted.
I would have thought, goign on the ph1&2 that the dials simply swapped over, you will know cus there will be a specific plug for the tacho, and if it aint there then it wont work