ok so looking like the wifes truck probably has the cas-tech heads on it and i've been hunting all over online for replacement heads and have run into an issue. How can i tell the difference between the gen 3 LM7 (323) and the gen 3 LM7 (325)? the 8th digit of her vin is T. also is it possible to swap heads between the 323 and the 325, incase i have no other options? And lastly, what is the best way of going about this? i dont want to spend alot of money so i dont really want performance heads or anything but i would like them to be complete. any help would be great.