ODBI or ODBII

i have a line on a 96 dodge truck with 5.9 but i have heard ODBII is better and i thin that started in 97 or 98, just wondering how it is better and if i should try and buy the truck, want to repeat BADASS's build and put the entire setup in to a 68 cuda, truck is suppose to be around $600 to $800 so sounds like a perfect fit. OOH i will be using a 727 instead of the 4speed auto in the truck cause it is a 4x4. any info would be appreciated.