(Apologies for necroposting…this seemed worth of a few electrons…) For what it’s worth, here’s my experience and opinion based on feeding several years with a Pi 3A+.
Opinion
It seems the Pi Model 3B+ is currently available at close to pre-covid prices allegedly new on amazon (US) and the Pi 3A+ is only a minor amount less than that. I’d go with the 3B+ and maybe buy a spare (in case it dies or gets shorted out). If you think heat would be an issue, I would add a small fan to the case as well as heat sinks.
The additional performance and power consumption of the Pi4 and Pi5 add zero value, especially for the additional price, over a Pi3 to my production feeder setup. I suppose a Pi Zero could function, but you would need to work at it and watch it.
Many have posted innovative and functional Pi enclosures. Ruggedizing (and cooling) might likely exceed the cost of the Pi.
Alternative
I have been e-cycling HP thin clients (story here) and had scored a deal ($45USD) on HP T630 units (wireless, TWO M.2 SATA slots, 8GB memory), power consumption 3-5 WATTS AC (amounts to killing an ant with an A-bomb 
) It would be perfect to stick in the garage for the reasons I mentioned in the story. However, I do worry about overheating, and the case is large (about 9"x10"x1") and likely would not survive the dirty environment. But something to look at as an alternative.
Background
I have a Raspberry Pi 3 Model A+ (512MB memory, 4 cores, single USB) with the blue Flightaware dongle feeding Flightware and a couple of others. dump1090-fa, piaware, tar1090, graphs1090 with a UPS backup board attached to the Pi. The feeder sits in a garage mounted on an open frame with no heatsink or fan, just convection. Consistent power draw 5.1VDC 0.35-0.5amps. I’ve run the feeder on Stretch and Buster-based versions of RaspiOS (32bit). As can be seen from the memory utilization graph below, it’s MOSTLY OK. I did leave swap space configured, since early on I notice swap was being used. The ‘risk’ of very slightly elevated SD card wear versus out-of-memory events is worth it to me. The same 32GB SD card has been in use all this time.
I ran a development instance of an upgraded Bookworm-based Pi feeder on a spare Pi 3A+/64-bit OS, and was disappointed to find more memory utilization, more swap use, so decided if/when I do update to v9 piaware, it will be on a Pi3B+ (double the memory) for a very slightly higher power use (measured as about an addition 0.1amp).
Memory utilization over time (I did not retain feeder performance info for before Sep 2020, moved)
CPU Heat profile over time:
