360, Yes, you can use the NAG1 even behind a LA small block. Your old trans set up would not be used, Sound German would be able to tell you what you need better than I could. I just talked to them before about putting behind my 71 318. I went with a 42RH instead as it was a lot cheaper at the time. The controller is a little pricey (about 1200) but if you get the trans cheap enough it may be worth it compared to a complete rebuild of a 46RH. Plus the gearing is a huge improvement. You are exactly right about the gearing. Send them an email and they will get the info you need.