Does anyone no what size tap is needed for the LIM to add a barbed fitting instead of the elbow?
I will be using a low alternator mount. What should i do with the coolant elbow that goes to the stock alt bracket? Do i tap it as well and add a barbed fitting?

There are many threads on this subject. If you do a search by "3800 coolant" you will find many of them. I think that if you tap the LIM you should use an elbow or nipple with pipe threads. I did not use the outlet in the LIM below the supercharger. Instead, that outlet is plugged with a freeze plug. I also plugged the return port where the other stock elbow is mounted. I run a tube off the filler neck (by the thermostat housing) to one of the heater core tubes. The other heater core tube is routed to a nipple on the passenger side coolant tube for the heater core return. You can use the LIM and the other port by the water pump, but I chose not to due to the tight fit with the fuel lines, injector wiring and drive belts.

Why not just run a hose off the elbow?

The elbow has O-rings on each end that go into the LIM and the alternator bracket. The bracket holds the elbow in place. It would not stay in the LIM under pressure.

Below the charger should be 3/4 npt. At the timing cover should be 1". Series 1 uses 1/2 npt and 5/8 npt(very hard to find)
The LIM is not that bad to do. The timing cover does not have a lot of metal around it. Easily cracked.
In both cases you either need to grind the ends of the taps to more of a taper or very carefully drill them out a little.
I would agree on using a threaded bib on the LIM. On the timing cover I would get the metal replacement elbow. Cut off the other end to put a hose on it. Make a small bracket, that bolts to the water pump face to hold it.
OR freeze plug the timing cover off and use the modified thermostat housing instead.
Most of this, has been from reading hear, 3800pro, and other GM forums. There is also some reading at the 4x4 forums. 3800SCs are popular there also.

[This message has been edited by cmechmann (edited 01-02-2014).]

Thank you thats what I needed to know.

quote Originally posted by mitchjl22: Why not just run a hose off the elbow?

I'm a dumbass.... I learned why you can't today. It blew off and sprayed coolant everywhere.. time to find a modified coolant fill housing...

You can buy a modified coolant fill tube or do it yourself. I bought a "bypass hose tube" from AutoZone ... Motormite #56399. It is for a Jeep, but had a 5/8" flared tube at one end. I cut off that tube end, drilled a hole in my filler tube and used a propane torch to solder it in place. My filler tube is not stock, but I have included a photo below that shows the heater hose connected to the tube that I soldered onto the tube.
http://s463.photobucket.com...tsupplyhose.jpg.html

You can also view a modified coolant filler tube in the following thread ... the photo of the modified tube is in about the 10th post. My filler tube is separate from the thermostat housing. A short radiator hose connects my thermostat housing to the filler tube. The filler tube on my car is very long (runs down almost to the driver's side coolant tube). I soldered in the flared 5/8" tubing lower in the filler tube, but it should work if installed anywhere in the filler tube.
https://www.fiero.nl/forum/Forum2/HTML/125666.html