looking to swap heads might have a deal on some 317's but heard that the 243's are better for the 5.3??? i won't be running any boost but maybe some nitrous later on. thanks

 

Your best bet would be to stick with the stock heads on a 5.3. Either the 317's or the 243's will lower your compression. If you want some more out of the stock heads just get them worked over a little and mill them. Richard from WCCH has some nice heads as well and he is a sponsor to the right. ---------->

 

I don't think you'll see any huge gains with new heads until you really get more air moving through that motor. I think you'll have much more bang for the buck going with a nice cam and a good set of longtube headers. Once you've gotten other essential mods done, then you could throw some money at headwork.