http://www.ebay.com/itm/Ford-Mustang-351W-roller-cam-distributor-for-swap-conversion-87-93-Mustang-5-0-/111114783133?pt=Motors_Car_Truck_Parts_Accessories&hash=item19def5099d&vxp=mtr
This should work if i am converrting my 1990 f250(Originally flat tappet) to a 351w with a roller cam right?

 

If this distributor came from a 5.8 motor then it's good, but be aware no EFI 5.8 motors were installed in mustangs(OK there was a CobraR with a 5.8 but there were super small numbers produced and for racing teams only.. none sold publically) and all truck motors with a roller cam would have used remote TFI modules, so if this really is a 5.8 distributor it's a custom creation.. which is fine but you won't know until you get it and measure several things.. the oil pump drive shaft and body are slightly larger than a 5.0 version.

FWIW if you were to find a distributor locally from a 5.8 roller motor('94+) it will have the steel gear and it's easy to modify it to accept an onboard ignition module. That flat surface that it mounts on is still there you just have to cut a slot to connect it to the PIP module that goes inside(the same module is used in the 5.0 distributor) and drill and tap 2 holes for the mounting screw. The other way around it is to get an early 5.8 distributor and put a steel drive gear on it, that may be what this Ebay listing is for.