Trying to print the extruder body for the taz and the .STL already has a support structure designed into it. For some reason, Cura does not print the smaller (repeating circles ) structure. When I view it in “layer” view, it also disappears.
The extruder body STLs provided by Lulzbot have supports designed into the object. So you should be able to print as is… no supports. For instance, the concentric circles in the last picture of your original post are supports. The tapered screw holes will print without supports…
I had to repair the model to get the supports to print correctly. 
Interesting, that you had to repair their model. I removed all the designed in supports and trusted S3D… removing the supports in SketchUp was no fun. 
To get the same exact part as factory, I’d probably chance the g-code with the appropriate nozzle diameter that they share on devel.lulzbot.com.
I am aware that it is designed into the object. My initial print was printing as is without adding Cura support and the supports didn’t print. My second print, I tried adding supports via Cura (touching the build plate) and that as well didn’t print. I have printed this extruded body before on a TAZ and the supports printed. I don’t know why its not printing now.
Try this one.
extruder_body_3mm5ex_v1.3.2_fixed.stl (297 KB)
I do tend to use the optimized gcode files they have available myself for several years now. But several months ago someone else had issues with printing that STL file and I found that the supports did not print correctly, so I put the model through Netfabb cloud and then it worked? It is ~300 bytes in size different, and I do not know why but it seemed to work for me then. YMMV.
Hmm… by chance are you using a .5 nozzle? Without going back to look at the supports, could they be too thin to print with the .5 nozzle?
I’ll dig up the original extruder body tonight to take a look. In the meantime, I’d give kmanley57’s fixed model a shot.
I am using the .5 nozzle on the Mini and when it did print on my Taz, I was using the .35 nozzle. Ill give the fixed STL a shot.
That file worked and it printed with supports. Thanks!