Alright let me start out onthe basic stuff first then the more indepth things.
1. first thing youll need is motor mount adapters so you can bolt up
to your stock chevy motor mounts.2 places that i know of http://www.hotrodlane.cc/
i got mine from dan at vetteworks.
2. next is wiring harness and pcm,alot of people order a harness already made for around $550,i think its a waste of money,i took a stock 99 fbody harness $75 and hooked up 5 hot wires and a few grounds.I made a separate fuse box for the hot wires.I bought a pcm from jesse at wait4meperformance who tuned it for me for what i had in the car plus had the vats turned off for the security.Started on first try.
3.exhaust theres only afew options out there fbody exhaust manifolds,or build your own headers or do what i did and modified my sidepipes and welded on ls1 flanges that i bought from the dealer for $15 a side.It takes alittle work getting the tubes to fit the new ls1 pattern and alot of trial and error fitting them in the car but boy does it make a ls1 sound great.
4.accessorys,meaning pulleys alt.power steering etc....try and stick with firebird or camaro stuff,i had c5 brackets first but not worth the effort getting them to work, i switched to fbody.Also oil pan stick with fbody pan ,i used a truck oil pan from a 5.3 had to cut it and modify it it was too low and scraped the ground on hard bumps.
5.fuel supply.you can do 2 things modify your tank and use an intank late model pump or frame mount,i did both and switched to frame mount now.Without baffles intank i ran pump dry on hard stop and killed a walbro255 pump.As far as fuel lines and filter,use a 99 corvette fuel filter/regulator,there combined,it has a inlet on one side plus the return comes right back off of it into your tank,then single 3/8 line going to fuel rail.i can get part numbers for that also.
6.ok transmission,this is your choice,you can use anything you want,turbo 350,400,200r4,700r4,5 speed 6 speed 4l60e etc...they all bolt up im using a 700r4 since i already built it up for my old motor.The ls motors use only 5 bolts to bolt the trnsmission up one on passenger side isnt used,dont try and drill it out either.It works fine with 5 bolts.Now if your using anything else besides 4l60e or a 6 speed then youll need a crankshaft spacer and 6 longer bolts from the dealer .Whats this does is help align the hub of the convertor into it,since the ls cranks are shorter.You use a stock ls1 starter also.
Now alot of guys want to do the swap but dont have tons of money ,all ill say is search everywhere for the best deals,the forum for sale sections,ebay,friends etc...i did my whole swap including building my ls1 from a brand new bare block for $1800.ls1tech is another good place for parts cheap .I basically did this swap on a budget to prove it can be done cheap not $5000 that i see guys spending.I have a 99 block,2004 c5 crank ,rods, pistons, heads,2002 ls6 intake and injectors and throttle body,99 harness and pcm.Hope thsi helps some and if you have questions just ask.