I need a new furnace in my 1955 house in CT. I was thinking of switching to gas heat... is this a good idea? I have no AC and was wondering if switching to gas might not be a good way to have AC along with a new system. Would appreciate any advice

Yes you can use gas in your house. I would contact 2 or 3 local HVAC contractors to get estimates before you buy. I would also have them do a fuel cost comparison so you have better knowledge of your utility bill.
I would also get there recommendation on a heat pump system for your home. It has many advantages for saving you on your utility bill.
Your local contractor will be glad to explain this to you.

I have a much older house that the previous owners made that switch. The biggest issue was that in order to enable AC as well as heat, the put in forced air venting throughout the house. This can be very disrptive and on an older stone house like mine, they had to make major changes to the structure of the house. Given that they never got around to putting in the AC components (as an old stone house, it never really gets that hot), it seems ilke a lot of effort for little gain.

I have heard about high pressure forced air that uses PVC pipeing instead of vents that has much less impact on the hosue, but I am sure others on this board know much more.