replacing old oil furnace with new propane hi eff.

What have I done

Ok I been working on this old foreclosed farm house for a while now. It has an OLD oil furnace (HUGE) with ductwork spidered all over the basement. the second story bedrooms only have 1 register in each room.

1. When replacing the furnace should I replace all the ductwork with a more efficient layout?

2. is it better with a 2 story house to have 2 seperate furnaces and central air units for heating and cooling. This is the setup we have in the house we currently live in. granted it is a lot bigger than the farmhosue we are redoing but it is AWESOME for cooling the second floor in the summer
In your opinions what is the best route to go before I start calling contractors and getting estimates

Should I re-use the existing ductwork? does it make sense to put in seperate units for main and second floor?

We are dealing with about an 1850 sq ft 2 story farmhouse. it is getting completely gutted so walls arent in yet and would be fairly easy to run new ductwork.
We are in illinois, fairly cold in the winter hot in the summer

redline

1. Yes - if you are able to.

2. With it only being 1850 sf then one unit should be fine. I would think that you will be insulating it before the drywall goes up - this will help with both heating and cooling efficiency.