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First question for anyone that knows: My son's 6 of '71 ('72) 240 is getting an R200 with a 3.9 ratio. When I went to service and make sure of the gear ratio, I found this: The main large ring gear is stamped with the 39:10 ID but what I don't get is the smaller internal gears; they're welded together. Is this a LS differential that has been "cured" of potential breakage? Secondly: I bought a T5 to replace the four speed. I think I should have bought a non Borg Warner five speed "Type B" instead, but I'm not sure. From what I've read through many a thread and blog in order to avoid sounding like a whiner who doesn't want to do the work, was that a T5 is better matched with a 3.545 rear ratio, or 3.7. The assumption that first and second gear will burn rubber too easily was met with approval from my son; strong approval. But I'd like to know any other concerns anyone may know. Is first gear going to red line the turbo we're putting in too quick? Second as well? I believe I've understood this potential as one of the drawbacks... I guess I could let him blow the motor and learn some more valuable lessons... The T5 is identified under the shifter with these markings: R1, then under that 13-52-066-903, the the Borg Warner markings. Under that but forward bolted to the housing is a metal tag reading: 052-004 space 24379 (I can't read what the number is above this on the tag...). Above on the top of the middle housing reads Basic 1, 13-51-097-901. Lastly, on the front section top reads 6Z 791 From what my son found on a link provided by another member, I believe, is that this BW was made for the 1983 turbo. We are putting in an '83 turbo. Thoughts and feedback are much appreciated.