Depends on the inletting of the Manners stock.
Timney for the 455 may require additional inletting.
Yo Dave will work, but a Rifle Basix will fit and
allows sear and trigger pull to be fully adjustable.
I would buy the Timney if I thought the yo Dave was lacking in any way. I tried the yo Dave because it was cheap and was very impressed with it. It will also tune lighter than the Timney.
I've had timmney and yo Dave setup. I actually prefer the yo Dave in my rifle. May try the rifle basix at some point, hard to argue with the cost/performance of the yo Dave kit though.
It is very hard to beat a shim and spring swap on the factory trigger. If you need it even lighter a little polish work and with a quality moly lubricant will lighten it even further.
I too am a big fan of Timney triggers, but in my 455 I have a yo-Dave. It has worked perfectly from day one, and now my daughter shoots the rifle. I have it set at 1.5 lbs, and we haven't had any A.D.'s in about 2000 rounds.