Grumman AA5 series....facts versus fiction question

Hi folks,

I was in the process of purchasing an AA-5A cheetah this week and
spoke with the owner about it. Pictures looked good and the specs were
reasonable for the price. Then I inquire about damage and use. NDH,
great. But then came the bombshell. I asked and he said that he sees
around 112-115 KTAS in cruise at a 23-2400ish power settings. My jaw
dropped to the floor. I asked if he had a Traveler instead of a
cheetah, he assured me a cheetah is what he has. Something is not
adding up. He was candid enough and asserted he could see me getting
120KTAS if you fly the thing wide open and he sure as heck has never
seen the book number of 127.

My question is this. I understand there is usually a difference
between stated book numbers and real numbers, but he confidently (I
appreciated his sincerity) asserted he would barely make 120KTAS with
the thing wide open, which for the purposes of this discussion was
validated by his GPS groundspeed with nominally no-wind. That is a 7-8
KTS difference from the book, more along the lines of what I would
expect to see out of a traveler, which killed off the deal, and
formally has me even reconsidering the Grumman line.

So what's the scoop from those in the know? Are Grumman book numbers
just outright bunk? Because I know I can get 115KTAS out of a 150HP
172, been there done that. Usually a 150HP 172 will stabilize in the
112KTS range, I can take than number to the bank. That is within 3
KTAS of the book, not bad for 30 yo spam cans. But when the cheetah
book advertises 127 and you're struggling to keep 120 something is not
right.

ANybody have any experiences with the cheetah. I was looking for a
125KTAS/150HP aircraft, which is the only airspeed/engine combination
that makes it worthwhile upgrading from the capital and operating cost
of my runout 95KTAS/100HP flaking paint Cessna 150. If I wanted a
115KTAS I could go with a 150HP 172 and have more wide service support
for the same money, yet it's not worth spending 2.5x the money to get
an additional 15kts. I was considering the Traveler line, but if the
cheetah numbers are so skewed, that means the traveler is really a
105KTAS aircraft, meh..

Thanks for the feedback