Cheapest liability insurance for my old 1978 Dodge van.

My next liability payment ($149.00) for the next six months liability
insurance for my old 1978 Dodge van is due before midnight of this month
before Feb 17.A guy who lives next door to me owns a 1987 Toyota pickup
truck.I was talking to him a short while ago.He says he pays GMAC
$100.00 each six months for liability insurance for his truck.I think I
need to look in my phone book and call GMAC.I used to have liability
insurance through Audubon, I was paying about $144.00 each year, but
Audubon stopped handling this state.I want to find the cheapest
liability insurance I can, my old van isn't worth more than that.I
hardly ever drive it anywhere anyway. 
cuhulin