One additional side note:
4 bolt mains are great but ;
1) you cant see them
2) Ford states that the 2 bolt variety is just as strong, unless maybe your racing at 8,000 rpm all day
3) The other guys are correct in the earlier date codes. Early heads make more power.
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Me personally: I would think that you would like to have it fast but
smooth.
If you dont have much experience like me on rear ends....take it to a pro speed shop that specializes in Ford nine inch rears and have then verify everything and check back lash adjustments before you do anything drastic like replace everything.
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Second suggestion on the tranny;
I personally would remove the tranny add ons and go back to maybe a mild shift kit and maybe put in all new gaskets and seals and be done with it. The ease of shifting and having a smoother ride I feel will more than compensate for a harsh dragster feel when driving it. You will likely enjoy it more and will likely finish the restoration if it runs smoothly and is more refined in how it feels..........just saying...opinion wise that is.
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Finally;
Make that car your own!.....it looks really cool.:thmbsupDo with it what you always wanted to do in that car. Don't cut corners....Have fun with it.