After much aggravation, I figured out the issue in assembling a Stevens Favorite with the extractor which has a plunger.  The key is to install the block screw first, then insert the extractor and lever.  Use a punch to hold in place then push the extractor back toward the block using a punch inserted though the front of the receiver until the extractor pops taking the tension off of the lever and extractor.

Good show!   I've always hated that task.  So much so that my sole 1915 Favorite has a plain extractor.  I kinda prefer it anyway, since removing an unfired cartridge doesn't involve picking it up from out of the grass.