I "cross the fence' at 70 MPH indicated(full flaps). 80 knots is about
92 MPH which is way too fast. You will almost certainly bounce at that
speed. The early models had the airspeed shown in MPH whereas later
models were in knots. There is some great, free advice and discussion
on this subject(and most anything else about Cardinals you could
imagine) at www.cardinalflyers.com. Keith Peterson and Paul Milner who
run the site are very Cardinal owners. Check it out. The secret to
great (meaning no porpoising or such) is to never push the nose down
once you are in the flare. Keep it level or above and everything will
be OK. Trust me, I have dropped mine in from great heights and that
steel gear just soaks it up. Just hold your nose steady and the bounces
soon stop. Start chasing it and you can be in big trouble pronto. Most
people used to 172s and the like are surprised by how fast the full
stabilator will react if you start trying to correct a bad flare, and
end up over correcting. Also, all 68 Cardinals were modified with the
stabilator slats at Cessna's expense during the first year they were
out. All models since then, 177A, 177B, and 177RGs had the slats from
the factory. Cardinals were much (undeservedly) maligned for years due
to this issue. Most people (including Aviation Consumer which loves
them) have finally admitted what a great plane it is (which is why I
actually went looking for one).
The 68s can be great buys since you can buy them much cheaper. An
acquaintance of mine has a 68 with your 160 HP mod, a Powerflow
exhaust, and a cowl flap speed mod that really does as advertised, and
his is as fast and climbs as well as a 180 HP model. Could be a good
buy if the price is right. Just be careful of gross weight.

Regards,
Bruce Cunningham
N30464