Yeah folks.I had a funny,sort of simmilar run in with one of the guys.

I used to fix lawnmowers and weedeaters for friends and kinfolks but it was a while ago.For the parts i usually drop by local john deer dealership.
So once i stopped there and they have a repair shop next door.It was 5.25 and they started locking up doors.When i walked in guy said"what u got?" i said "it's not what I got but rather what YOU got" he looked at me like i was nuts.Thats what i wanted.I asked him if he can give me or sell me any small engine running or not as long as it got carburetor and coil on it. He told me "yeah,look at this pile." I told him " i don't care what engine or what brand.Just reach and pick one up.He reached and picked up 46 cc poulan chainsaw with no top nor anything else but magneto,carb and engine hanging there on one bolt.He told me"give me $5".When i was leaving he kinda sarcasticly asked "It aint worth restoring it".I bet he though he made a deal of a century LOL. I put the saw in my truck and told him "nah,I will just use it as alternative to 350 dollar engine in my model airplane. See ya."
A few months ago i bough a perfectly working ryobi trimmer for $15 using the same technique . I almost finished converting it.
Bottom line is it never hurts to stop and look and talk with guys but i wouldn't just mention right off hands that engine will be flying airplane.Unfortunately psychology of the sale people is this:He gonna use it for hobby.Hobby stuf is $high.Then this engine is high."
Instead tell him you buy it for parts or out of curiocity to see what's inside. You'll get a better deal.I guarantee it.