i just recently got a 54 merc 256 4 barrel manifold that im gonna run on my 239. its setup with an adapter and a new 390cfm holley. from what ive read, i have to switch to a 57 + distributor, swap the drive gear over from the old distributor and switch the oil pump as well. Is this all i need to do? anything else ? also are there any particular distributors anyone recommends. any help is appreciated. thanks