What would they be worth?

I say the bottom line is $500 for the pair as is.
If the 340 is a good core, then you did good, and if it's a dud, then there's still the heads etc. that are worth some money.
The 318 isn't worth more than $100 as a core at best, and that's if it's good.
It's called gambling, you win some, and you lose some.......


I certainly agree with the gambling part...and the odds are not on your side with the amount of information on the engines currently available.