Hello everyone, I have a qusetion for ya and this is after hours of searching for the info myself online with no luck. I have a brand new Heil ultra high effecient DC90 furnace ,that I snagged for $100 still crated its rated at 125,000 btus which is going to be a little bigger than I need but for the $100 I am going to use it as I am in a very rural town a 100 miles away from any HVAC store... sooo, I need to know how many sq. inches of return air grill to install and how many sq inches or vents to install and sizing of the ducts. I want to get this correct as undersizing will cause stress on the blower motor and heat exchanger and cause them to be short lived. if I had to guess I would say my house is just shy of 1000 sq feet with 9 foot celings, I know I know kinda small for the btu but I believe I can make it work with the right duct system and the unit will probably only run for short intravals at a time. I have 2 bedrooms, one bath, one living room, one kitchen, and one dining room I planned on a tottal of 7 vents so I might need them to be larger to let the unit breath.... if you can help or point me in the right direction that would be great thanks.

blower motor specs are 3/4 horse 1075RPMS
Also house has no exsiting duct system so all will be from scratch.