I wouldnt use the 4:1 sewt up, I would use the golaith one that is 2.7:1 since its more for bigger motors. But with that setup it would give me a crawl ratio of 102.48:1 Not bad. I have a th400-203 setup already, but then I loose OD and then I would have to regear front and rear to something like 3.73s and then do the 3.6:1 low for the 203 to make it close to that low of a ratio, but it would still only be 66.6:1