8:00 am ET is not suitable to schedule meetings
When planning a call between Eastern Time and Mountain Standard Time, you need to consider time difference between these time zones. ET is 3 hours ahead of MST.
It is currently 8:00 am in ET, which is not a suitable time to arrange a call or meeting with someone in MST, since it is 5:00 am there, which not within the optimal time span between 7:00 am and 11:00 pm.
You could, however, schedule a call between 10:00 am and 2:00 am your time. This time span will be between 7:00 am and 11:00 pm in MST.