Is it permissible to purchase a truck from an Islamic bank that first buys it and then sells it to me in installments after agreeing on the details?

As long as the bank will buy the car and own it before selling it to you, there is no harm in that. It does not matter that you are the one who identifies the car and agrees with its seller on determining the price and so on. This type of contract is called Murabahah for the one who commands the purchase, and it goes through three stages: a promise to purchase, then the commanded party buys it, so it enters into his possession and responsibility, then the commanding party buys it from the commanded party.