built 350 or stock 400??

i got a 91 chevy silverado z71. i plan on pulling it off the road soon to do some work to it. the motor is the biggest issue as of right now. it has a 350 efi in it. it has been bored 40 over. but thats all thats been done to it to my knowledge. its been running rough lately so its gonna need to be rebuilt if i decide to use it. i just got the chance to buy a 400 small block. its all stock with low miles. its been sitting for over 10 years so it would probably have to be cleaned up, so i would rebuild it to use it. my plans for the truck are to make it a trail rig and part time road truck. i wanna a little more power so i don't know which engine would be the best pick. i want decent gas milege but its not a big deal. any thoughts would help. thanks.  

you cant beat cubic inches. a 400 probably isn't going to get better milage than a 350 but if your going to want to make it an off road truck i personally would get the 400 and clean it up and maybe put a cam in it. but probably not to radical of a cam unless you want to spend the money replacing parts that will handle a large cam. just throwing out an opinion  

I have a 350 and a 400. I like the 400 it has more torque  

ive got a rank 350. its .60 over flat tops, cam and dual plane...i use it becuase i can get parts for it hell of alot cheaper than i can my 400. my 400 has a small cam, roller top and bottom and thats it becuase to buy replacement parts, its a bit more expensive but in a 4wd truck its all about the CID  
1985 C10 silverado. converted from a C10 2WD auto SBC to a K30 4WD 4SP BBC POWER STROKE? DONTCHYA MEAN POWER JOKE?

if you are gonna be on the road more than offroad. id say the 350 and like cowboyup said 350 parts come way cheaper than the 400. If you are gonna be offroad more than onroad id say the 400. i have a chevy blazer with a 400 in it for my truck and im usually more offroad than on road i love it.  

350 with a 400 crank a.k.a 383 stroker