12 bolt rear end

Hello guys.  I am new to the forum here and any help would be much appreciated.
 
Right now I have a 67 Camaro with a 327 and a 10 bolt rear end.  I am not sure on the transmission.  I was told it was a TH400 but it could be a TH350.  If have heard you can use the 10 bolt, but a 12 bolt is a much better option.  what do you guys think. 
 
I would also like to know what gears you would recomend.  The car would be mainly for the street with an occasional trip down the track for fun. 
 
Thanks in advance for your help.

How important is cost?

I've raced similar cars for years. Any thing beyond a 4:11 will be dificult to drive on the street. The 10 bolt will probably work with an auto matic. If you run slicks
over 28" you will blow the spider gears. The spider gears are the weakest link in the drive train. How fast do you want to go?

MnM7981
I am in the same spot. DTS and others told me a 10 bolt would be OK with street tires. With a auto as long as you are not to hard on it. No back to back burn outs (don't heat up the tires)
I would not go to the track with a 10 bolt.  I was told when a 10 bolt goes so does sheet metal. ( Fenders)