At one time my club operated three L-19's (actually two Ectors and an ex-RCAF L-19 to be precise). We sold one Ector to the Canadian Air Cadets a few years back as membership dropped. As we have no hangar the all metal structure is pretty much a necessity. We've never had very much trouble with airframe components wearing out or breaking in normal use. Most of the expense has been related to the engines. The O-470 family in general is pretty common but the O-470-11 as installed in the Bird Dog isn't. Continental doesn't support it anymore as far as I know and we've found quite a few shops won't even consider doing an overhaul on one. I notice Air Repair quotes about $23K if the exchange cylinders, crank and crankcases are useable which is in line with what we've paid in the past. If it has the original fuel system you're looking at $2-3K to overhaul the pressure carb. A while back we converted our L-19 to a standard carb. The Ectors already had them. We've experienced considerable downtime now and then trying to locate replacement engine accessories (sump and oil cooler spring to mind). Although there's not an official recommended TBO we've found that at 1500-1600 hours the engines are pretty much done.

The only airframe issues I can think of that have come up due to normal operating wear in the last 15 years were some cracked main gear axles, a tailwheel breaking off and some recent flap motor trouble on the one with electric flaps. We operate from a grass strip which has been fairly lumpy at times so the axle and tailwheel problems may have been a result of our particular circumstances not a weakness in the design.

There's no STC for a Tost hook as far as I know but we installed them as a minor modification.

The O-540 STC sounds intriguing for towing. The extra power, easier and cheaper parts availability and possibility of longer times between overhauls may make it worth the expense if it's currently available.

Quite some time back we ran the numbers on estimated cost of the L-19 versus a Pawnee and found in our case that the expected lower running cost of the Pawnee would be offset by the eventual need to replace the fabric. As the L-19 also has dual controls and all the towpilots found the Bird Dog more pleasant to fly we stayed with the Cessnas.