I understand it can be frustrating but don't forget it wasn't that long ago that swapping in an LS was freaking magical... as tech becomes more and more "common knowledge" we tend to forget how much was involved in paving the way for this stuff.
If anyone told you an LS swap was a bolt in and go Sunday afternoon project they lied. It's MUCH easier than it was just a few years ago but there are so many variations within the blazer/truck/suburban '73-'87(91) that nobody should guarantee a "bolt in" install without expecting some minor hiccups in the road.
You can check out the truck I was talking about here. LS swap starts around post 82...
http://coloradok5.com/forums/showthread.php?t=301539&page=5
Best of luck to ya! You've got this and it'll be worth it in the end.