Holley makes a complete kit for an LSx swap. Cathedral port motors (Gen 3 LS) are significantly cheaper than Rectangle port (Gen 4) motors but the vast majority of the related parts are interchangable. The first post in
My Swap Thread (click here) describes my original plans.
You can realistically do a 5.3 swap for 5k on a mustang if you're doing it yourself. This build is for a 6.2L (figure looking at around 8k if you can do it all yourself. This is not a starter job. At bare minimum:
L92 or LS3 engine (these are basically the same engine, the L92 and LS3 share the same 6.2L bottom end and make nearly identical figures)
Gen 4 LS Swap 96-04 Mustang LS Engine and Transmission Mounts
Holley Sn95 LS Swap Oil Pan 302-1
Flowtech Sn95 LS Swap Long Tube Headers 1 7/8" primary to 3" collector. Name brand (they're made by holley as a low dollar alternative) LTHs. You don't need to go that big but it's that or 1 3/4". 1 7/8" seems to be the go to.
You'll want to get some sort of header back exhaust but that's on you. At stock L92/LS3 power levels a dual 2.5" exhaust setup will likely suffice.
You will probably need an in tank fuel pump upgrade to keep up with the demands of the LS over the 3.9L v6.
Do yourself a favor and use at least a 6 speed auto. 6L80 or It'll cost a bit more up front, but it will be far and away the better choice. Better gas mileage, more time in the power band, you're driving an auto so shifting more often doesn't matter, and it'll be faster everywhere. I always reccomend learning stick if you don't already but I'm guessing you have an auto trans car.
