if you got a 225 slant 6 3spd 1974 Dart or somthing like that, it's not worth much.. Chevy wouldn't hurt the value but it won't gain value.. your only gain would be more power easier.. turbo'd 225 can do 600 HP on the right setup tho.. however, a 318/360 will be the same cost, or a little more to build than a 350 SBC in the same flavor.. BUT, you will have less fabrication and fabrication costs being it will almost bolt in.. as well as not being hacked up it will increase value... if you have a 318/240/360 powered Dart arleady, then it is kind of a waste to even consider a brand swap..

and if you have somthing like a '64/'65 Dart.. then it's kinda stupid anyway. being the 6cyls are worth at least $5-8k buildible