I just took out my old F motor and tranny. my body is off the frame so its great working conditions. I have a early 70s rebuilt 4 bolt 350 and am weighing my options on what I want for a new tranny. I know most people go with the SM420 or SM465. I will not be rock crawling and will not need the benifits of an ultra low gear. I will be going through mostly mud and snow and prefer a automatic in these situations. I hate running out of a gear when using a manual. Does anyone have any experience with this? I did a search and found nothing. thanks