Up at the top of this page is the main banner, bottom part has links to Ranger info.
Tech Articles link will help you alot.
http://www.therangerstation.com/tech_library/index.shtml
Look in the Engine section, several V8 swap articles posted by members are there
3.0l transmission(M5OD-R1) won't bolt up to 302(5.0l) engine, and wouldn't last long in any case with the extra power.
'78 trans shifter will most likely not be in a good place for use in B-series floor pan, but can't say for sure.
M5OD-R2 transmissions from '97-'01 used in F-150's with 4.2l V6 will bolt up to 5.0l and has shifter near current B-series location, you of course would want a 2WD trans.
If you stay with carb and distributor wiring will be pretty basic.
You will need to lower the fuel pressure with a regulator.
'95 B-series also didn't use speedometer cable it used a VSS(vehicle speed sensor) on the transmission, so your speedo/odo is electronic, the trans you end up using will decide what the best way is to get signal to the speedometer.
If you have ABS then you may have a VSS on rear axle, and it can be used.