Okay so after doing some research you should need a 26 tooth, 6 spline bull gear. My spicer 18 has a 1 1/8 intermediate shaft I think and the bull gear is a 26 tooth, 6 spline. The Dana 20 I have is a 26 spline, 6 spline bull gear as well. They both fit my t18 output shaft just fine. They do look a little different in the picture but they fit the shaft the same. So I THINK you need a 26 tooth, 6 spline bull gear. Novak has a gear interchange on their website. The gear on the left is from a 1 1/8th intermediate shaft spicer 18 and the gear on the right is from a Dana 20. I had an issue uploading the image. Hope it comes out okay.
Novak link: http://www.novak-adapt.com/knowledge...gears_grid.htm