Ross Richardson wrote:

It could be a C-172 with the Avcon/Doyn/Bush conversion. I have a '65
Skyhawk that you describe very accurately. The "bumps" are clearance
for the cylinder heads since the STC holder did not redo the top
cowling. They are made of fiberglass and riveted on.

It could also be a C-170 with the 180 conversion. If the vertical
stab was round at the top it was a C-170. Square or slanted it was a
C-172. Those two are pretty much the only Cessna types I've seen with
the cowl bumps.

John Galban=====N4BQ (PA28-180)