ls1 347 vs 5.3L ?
edit: now that i have re read your post, the only way i would swap out the short block is if you have the iron block LM7. other than that i would put the stage 2 5.3 heads and the other stuff you have including cam and call it a day. its all gen III engine stuff so it will all coexist.
that right there should be enough to point to which one makes more power (CIs people.....)...
then to top it off, the iron block is ~80lbs heavier.....
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I have an 01 Silverado with the LM7 5.3 as well. About 207k miles and still chugging along with no complaints
.When it gives up, I plan on going with something like this:
http://thompsonmotorsports.net/onlin...products_id=44
and topping it off with some 243 heads and a LS6 cam or similar.





