RE: Q about Jennings devastator crossbow
As Cos notes, because of the design of the stock, nuthin's gonna work rightout of the package.
You're gonna have to go to the crossbow sites, look at their crank mechanisms, buy what you think will work, then adapt/modify it yourself.
I'd guess...it's not as difficult as it sounds. A few hand tools, and a coupla hours work, should be good.
Have fun.
Mike