Engine 165 for it's location and road network, if you focus on SI. If you would want a location to be able to respond into parts of Bklyn, then a FH location closer to VN bridge is better.
There really should be a squad on SI, somewhere. Think of how many special units a city or county fire department of SI's size usually has in other places. 500,000 cities usually have more than 1 rescue company. Raleigh NC FD (276,000 population) has 3 rescue companies. Arlington County, VA, FD (population 207,000) has two heavy rescue companies. SI has Rescue 5.
By the way, is Squad 1 in the best location to cover SI? (20-plus mile runs)