Jeredk21

I am looking at buying some 243 heads for my ls1. I am still learning my engine. Is there a difference from the z06 243 heads and the ones off of the ls2. I found a set from an ls2 I was gonna buy. Also can I just bolt them on? Or is there other changes that need to be made too. Next I will be looking at moving to headers and swapping a cam.

IRON MAIDEN

Same heads. 243/799 castings. But the LS6(Z06) had hollow intake and sodium filled exhaust valves. Believe that is the valve arrangement. Either way, they had lighter valves. I went with a set of 243 heads off an 08' 5.3L truck engine. Sent them to Advanced Induction for their cnc magic.
Get the set off the LS2.

NukeC5

Direct swap, but you will need the valve covers too, yours has perimeter bolts I think, and you need the center bolt.

LS6 heads are better if you can get them for a good price. If not, LS2 heads are great too. You can also get 799 heads which are the same as 234 heads.

IRON MAIDEN

Better from the factory only due to the light weight valves and better springs. The castings are the same. If you plan to bolt it on as is from the factory, the LS6(Z06) version is by far the best as NukeC5 said.
If you plan to have them ported and such, kinda doesn't matter at that point. Although having those valves would sure make me smile.
Like I mentioned, I bought a set of 243 heads off a truck motor so it has the same valves as the LS2 or any other 243/799 head. Only the LS6 243s got those light weight valves.
I was kinda bummed I didn't get them so I thought about just getting aftermarket valves. So I asked Phil at Advanced Induction about it when we were figuring out what we were gonna do to my heads. He told me to not waste the money. That the factory valves are good and strong. So I left them and just spent a little more on the BTR dual springs w/ Ti retainers, and Viton seals.

IRON MAIDEN

And I have a 97' so I had the perimeter valve covers as well.. Something NukeC5 didn't mention, is you will also need coil brackets with the covers. The coil packs on the 97'-98' C5's mount directly to the perimeter covers. No coil bracket used. Center bolt covers use a coil bracket to fix the coils to the covers. Also, pay attention to the pcv setup on the covers. I'm changing over to an LS6 valley cover, and 08' 5.3L truck valve covers which has one nipple on each cover. I plan to split the fresh air feed off the throttle body so it feeds fresh air to both valve covers. Then run the dirty side air off the LS6 valley cover to an oil catch can, then to the intake.

78GEN3

Iron Maiden, just be aware that you will have to clearance your block for the LS6 valley cover.
I just did the same thing you guys are talking about on my 97. Luckily my replacement block was a LS6 so I didn't have to clearance anything.
I mounted my original 97 coils to the new brackets with no problem and I used a set of valve covers from a 2002 5.3 truck. The brackets are fairly cheap like $10 ea. I put the LS6 valley cover and coolant pipe to make way for a intake swap later on.

IRON MAIDEN

Well aware of the required notching. Minor thing to do for a better pcv setup.

RedZMonte

be a good time to swap the 01+ ls6/LS1 style intake manifold if you are still using the old style LS1 intake.

If you get the LS2 heads they are the same springs as the 04 LS6 (updated, dont crack like older LS6) otherswise i would do the LS6 BLUE (LS2) springs at the same time with the truck heads (799)

S