1997 SSEi Tranny question

Hello all, I am looking into replacing the tranny in my 97 SSEi, but am wondering what the difference is between the 97 GM 4T65E HD, and a 98 4T65E HD? I was also told that I could use a 4T60E in my SSEi as long as I took out the HD differential from the 4T65 and put it into the 4T60 tranny??? I bought this car a few months ago and would really like to take it for a spin so thanks for any info.