I have a 2005 4 door Tacoma 4x4 TRD Package. I'm going to put a flatbed on it and wanted to know how much clearance was needed between the top of the tire and bottom of the flatbed?

 

Same as you have now

 

get as much weight as you can reasonably in the bed, measure the distance from the axle to the bump stop. whatever that measurement is, you'll need that much space plus like another inch or 2 above the tire. That way if you ever fully bump the truck out, you won't hit your tires into your bed, you'll still let the bump stops do their thing. Remember rubber bump stops do crush a fair amount.

 

Plus if you ever go up in tire size you'll be glad you left that room.

 

And articulate it fully in a dich or ramp. And take measurments off the frame, then compare to your flat bed build. SCToy has good advice, but the tire can still go higher when articulating then it can under level suspension compression.

Its time for a cave man drawing to explain

 

Good thinkin thatguy!