There are not many shops on LI just for trucks. RMS Offroad in Bohemia does good work but does not have a lot of stuff in stock that you can touch yourself. There is also a place called the truck shop in Sayville. Ive never been to it so I cant say anything about what they have there.
Most Jeep stuff is all mail order. Order it look at it and send it back if you dont like it. Its stinks but thats our only options on LI.