Regardless, why would you want a 180HP engine on a 150?
Harry Delicker at Del-Air says it's his most popular STC for the 150. When we were putting together my 150/150 STC kit, he told me that there wasn't much call for the 150HP STC. Most were going with the 180HP STC. Most of the STC parts are the same, with probably the engine, propellor and baffling being different. I wouldn't be surprised if the cost of an O-360 wasn't significantly higher than an O-320. Especially when figuring out how much the whole conversion is going to cost, going for the extra HP probably makes sense... at least on paper.
I decided against the 180HP version because of the higher fuel burn of the O-360 engine and the decent data on the 150HP conversion that lead me to believe that 150HP would be more than sufficient for my desires.
150HP turned out to be everything I wanted it to be, and then some. And the fuel burn isn't as much of a concern with what I've learned about operating my 150/150.
A friend at work flew gliders near Avenal, Ca., and there was an Aerobat with a 180hp engine as a tow plane. He said there were serious overheating problems with the plane...
Well, there is that...
I have to watch the oil temps pretty closely on mine in the summer. I think it has a lot to do with the high DAs I see here in CO that time of year. I've noticed that at lower elevations, such as when I go to Clinton, the oil temp is much less of an issue even when the OATs are similar to what I fly in at home. During the rest of the year, the oil temp is not an issue. There seems to be a direct correlation between the amount of throttle and the oil temp. Pulling the power back is the best thing I've found for keeping the oil temp away from the red line. I can imagine that an engine that produces more power would produce more heat and thus, higher oil temps.
It's probably just as well I went with 150HP. I certainly have no regrets.