what transfer case should i use?

I have a '86 chevy silverado with 350ci 400 tranny 14 bolt rear and dana 44 front... i am currently running a np208 case but i have a parts truck with a dana 20 bolted to a 400 tranny... i'm having a 4x4 shift kit installed in my transmission and seeing as how i'm gonna have it outta the truck i thought about putting the dana20 in while i'm at it... it is a daily driver and i mostly ride off road no major mud playing or hill climbing... any toughts or advice will be appriciated.  

dont they have low gear sets for the 20? guys?  

People use Dana 18 gears with the early Ford Bronco Dana 20 sliding gear to get a 2.46 lo-gear Dana 20.

What would you want to accomplish by using the 20 instead of the 208? Lo gear in a 20 is 2.0 and the 208 is 2.6, so that would be a disadvantage. The 20 is very strong, but the 208 is strong enough. The front output on the 20 is closer to the center which might create drive shaft to transmission pan clearance issues.

What is the TH400/Dana 20 combo from? Are you sure your front is a Dana 44? If it's stock it would be a GM 10 bolt. GM didn't use a Dana 44 front after '78.  

yeah i'm sure it's a 44, the truck it came out of was a '77 3/4 ton camper special with a 350ci 400/dana 20, i shouldn't have clearance issues seeing as how it's basically out of the same truck i'm puting it in.  

Well, it is a very common occurance to have clearance issues with the front drive shaft and Dana 20 and Dana 300 t-case when used with a TH400. People end up clocking their t-case down, or having special drive shafts made that use a special yoke and/or pillow blocks, or offsetting their engines to the driver's side.

And I'd never say never but I'd be very confident in saying a Dana 20 in a '78 K20 isn't stock. GM used a few Dana 20s in the First Generation K5 Blazers, but even those were not the norm. '78 had 203s or 205s.