Worth it?

Well Jack sold me the car for an awsome price. The body is in amazing condition (other than a dent in the front left fender), Almost no rust, The subframe and under carriage is in awsome condition, some surface rust ofcourse, but solid as the day it came off the line. Definatly worth the engine, its just a matter of application vs. cost. Hell I may even get that engine for free. My dad owes me a few houndred bucks still. What I’m asking is, is it worth the cost of the top end kit as opposed to like buying everything separate? I would like to be in the mid/low 12s NA. So would that be worth it, or would I be better off saving and getting a better engine? Like I said, the only reason I ask now is becuase of limited time to call dibs on the engine, and he wants to know whats going on so he can get the truck out of there. An LS1 would be nice, but its alot more than 1800 for a decent one lol.