I am trying to identify the transfer case I currently have in my Willies Jeep (60's) ~ the only number I can find on it is C18-15-10-3 almost positive it's not stock in jeep. Also, Any suggestions for putting a trasmission in the jeep? Was looking for automatic tranny options, but don't want to stretch jeep to make it work. Any ideas? if not, any ideas on what type of manual? Need lots of help!!!!!!!!!  

Sounds like a Dana 18. A 18 is easy to ID because the outputs are offset to passenger side while a Dana 20 that was starting to see some usage from factory in 63 was a straight thru drive design for rear axle.  

Sweet! Thanks, you've hit it right on. Any ideas on what type of tranmission this will work with?  

This is a little tricky in that a D18 generally had a 6 spline input and this was used with a T86 or T90 3 speed manual. (a T15, a HD 3 speed used with early to mid 70's V8 jeeps should work too as should a HD 4 speed T18 or T98) D18 used with Buick V6 and AMC sixes used a T14 which had a 10 spline input shaft to match T14. The 10 spline is kinda the bastard spline because 6 was more popular until jeeps when to 23 spline as new standard around 1980 with some mid 80's to 2000 4 cyl Jeeps using a 21 spline setup with LD trannies.

ALso let me muddy water a bit more. It seems that there was 5 different versions of D18 with different intermediate shaft diameters and input gear diameter. The really early ones (which you should not have unless it was swaped in) had a 3/4 inch shaft and a 1.98 low range at first then secon gen was a 2.46. Later models had a 1 1/8" (3rd gen) or 1 1/4" (4th gen) intermediate shaft and a 2.46 low range. 5th gen is last version and they are easy to ID in that they have a 4 inch hole in case for input gear while 1st thru 4th have a 3 inch hole. The nice thing about having a 5th gen case is that it share bolt pattern with D20 so you can bolt a D20 in place of a D20 tranny wise or use trannies from D20 to bolt to a 5th gen D18. You "might" have a 5th gen D18 but likely at least a 4th gen one. Have I muddied the water enough for you yet?