Which LS based engine to put in my chevelle?Bang for my buck?

[SUNK69]

I would like your opinions on which engine to swap into my car .I am trying to make my mind up on going with a 6.0 out of a truck or an LS1.My real choice would be a 6.2 or LS2 but that just isn't in the budget right now .I will be putting this engine in a 68 chevelle and haven't decided if I should keep the tranny auto or use a Tremec so you can give me your opinions on that also.