I am sorry but what seems to be the issue?
The ad states "I just removed the original strong running 400/350 from my 1971 impala! Its a little dirty, with 109,XXX miles. 4bolt main block, two barrel carb. price includes engine,trans,dist,exhaust man,waterpump! thanks for looking"
Does it not run strong?
Were you expecting a new engine for $800.00 plus the trans?
It has over 100,000 miles.
For a complete engine and trans I think what you paid is in the ballpark, considering I have seen 400 blocks bare go for as much as $500.00.
Did he misrepresent anything about it not smoking or that it was a rebuilt engine? Is it a 4 bolt main? Did he tell you it had no knocks?
Had he checked the oil for metal filings?
When you drove down and picked it up di you check the oil on it for metal?
I would have pulled the pan and tried to hook it up and test fired it.
Were you just going to run this motor as is or did you plan on rebuilding it?
Please clarify where he has misreprented what he sold to you.
Thanks
Edit...added to response