To the OP. I have done a lot of towing things.

IMHO if you put in a good five speed od tranny you can tow whatever the car will feel safe with weight wise with the stock rear end.

If you feel it has to be changed you change the diff. later with minimal lost effort.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.