Converting 1986 Chevy 305

[New To Propane]

I am new to the conversion process but I think I have enough of a mechnical background to make the changes needed. I think. I have a 1986 Chevy 305 in a 1/2 Pickup that has a carb and no computerized engine controls. I know in my area that the gas company converted thier trucks to be both gasoline and propane back when they used this year truck. What is the average cost for a conversion? What is a good source to get the parts needed to make such a change? What are the down falls to converting an everyday driver to this fuel source? I am located in the northeast of the US and would like to drive my truck this winter using this as its fuel source.

Thanks to any replies to this message since as you can read I am new to this whole thing.