Slant Six to Big block Engine swap in a 74 dart sport.

Thats a relife there would be nice to keep the power steering i'm not exatcly built like rambo.And another thing I was looking at through the day its already set up for hei so when I drop in a bbm could I just get a hei dist.or would I still have to get that kit made by proform.And could I get by with the stock rear diff or would I be better off with a 8.75 i'm not too concerend about the tranny the same guy at work buys 727 and sells seems like every mopar around her that has had the tranny swap has his tranny think he builds em to stock specs or would I be better off spending the 1200 on a beefier one by TCI?