Ok thanks all for the help. I did some research last night and found some SST (Sweet Spot Training) info that seems to be exactly what everyone is saying. Sadly my Garmin doesn't support any monitors HRM only syncs with my watch. I may get a monitor that works with my phone and record the ride on strava just to review the HR info after the fact.
Early on I would watch my HR often and found around 150 is what I can sustain for a long period of time and what I felt comfortable at when I rode for more than 1 hour. I breath hard, but I'm not out of breath. During a long ride with a group of other riders that set the pace at 20mph I was able to keep up with them for about 30 minutes before being dropped as we ended up going over a few med sized hills that sapped my energy at that pace. I noticed my HR was a lot higher than 175 so I guess my LTHR is 10 below that?? The odd part is when I crash and die and I'm forced to pull over and rest (happens often on hills) I look down and my HR seems to be 182-185. The highest I've seen it was 187. This is about when I start feeling nauseous and dizzy and learned to just pull over to avoid puking.
Looking at a SST chart it seems to be about right because it says I should be around 158-175.
The next time I ride I'm going to try and see if I can keep my HR around 158 the entire time to see how that feels.