if im not mistaken with the diesel being mechanical my speedo and tach wont work either?
Yeah, not quite sure about that one. I think it might, as long as the factory computer is left intact, even if there isn't an engine hooked up to it...maybe someone else that knows better will chime in.
To find a 4bt look for a bread van. Sometimes you can find a bread van (used also by Fritos and other short delivery companies) for roughly $3000 and scrap the aluminum body to make up some of the purchase price (I've done research on this exact swap and read what other people have done). You can also find adapters to mate the 4bt to a standard Ford transmission, such as the ZF, found in late 80s+ fullsize pickups, some of the breadvans already have this adapter and are running a "Ford" transmission, NP435, IIRC. Others of the bread vans run GM transmissions.
To fit the 4bt into your Ranger, you'll probably want a body lift to clear the top of the engine (from the hood) and a suspension lift so the differential doesn't hit the oil pan (they're pretty tall engines).