I just sold a standard bore 70 block (strongest year) at the local swaps for $150. I paid $100 for it almost 10 yrs ago, it has been sitting since. Cleveland stuff was worth more back then, I hoped for a better return, but C stuff is in decline.
I don't know the shape of yours, but mine was tanked, painted, and ready to go back standard. If yours is borderline, or HAS to be bored, I don't know what you would get. One thing is sure, you will get less having it bored, even if it needs it.
I guess what I am saying is:
If you bore it, you pay for the work and get $X amount.
If you don't bore it, you don't pay for work and get the same amount.
Dave