you buy an LS1-T56 on ebay for $3k (try to find one close so you can pick it up and not pay shipping)

you will have to get a high milage one since the low milage ones are fetching $5k and up

things you will need:

Full LS1-T56 combo with computer
welder
welding skillz (yes you need enought to pay the bills)
misc. bolts
LS1 engine mounts
T56 cross member
Grinder with a metal cutting wheel
1/4" thick steel plates for welding and cutting
Really big hammer for "massaging" areas of interest.

If you do it all yourself you will be right at $5k