I'm thinking of going with the GM847 what else will I need?
New springs, lifters, and injectors?

Going with LTs and true duals on the exhaust side and a tune.

 

with that cam, ur gunna need some ported heads its not gunna perform too good without heads,

You will need 1:6:1 ratio roller rockers, roller lifters, hardened pushrods, double coil valve springs. other stuff like gears, high stall or M6, a good tune, mail order tune might not cut it. freeest flowing exhast u can get, nooo cats

umm......anyone else wanna help out or correct me

 

it will run fine without ported heads....it will not be to the cams full potential but people are making 350+rwhp on this cam with headers,exhaust,and a GOOD tune.

 

just make sure you have a beefy valvetrain as too not have to wory about it down the road. If your doing the heads go ahead and throw some stainless steel valves in there as well. A good mail order tune from pcmforless will work very good. If your not satisfied with it after that you could just take it and get it dyno tuned.