cost to rebuild

I'm looking for a 94-96 caprice with a 5.7 liter engine right now and looking for low miles. my dilemma is i've found a few with low miles on the engine but the condition of the rest of the cars arent too great but i have found a lot of cars with higher mileage (80-100k) and the body's and interior look brand new. i was wondering how much a rebuild would most likely cost me. i wouldnt be doing the rebuild myself because of lack of resources and time so it would have to be done by a mechanic. what would the average cost be? i live in the LA area if that affects the price at all.
thanks