Yes, the after market has about an inch more drop in the comb. (I have one)
But ya might as well go to the source and cut out the middleman. Track buys their stocks from Pecitonica River Long Rifle supply. Might save ya some $$ unless Track has one that's a second or a sale,, I'd give them a call to confirm the drop and shape ya want.
http://www.longrifles-pr.com/ Just a tip, those stocks are a long way from "drop-in", I mean the TC stuff will fit with all but a little finish inletting, but theres alot of wood that needs to come off before you do the finish work.
I got a #3 curly from a member here for $75, he didn't have time too finish it. I have it mostly shaped, but it'll sit now till winter (again).