olds307 and 403 said:Get a 5.3 or 6.0 LS. Unless a decent sbc comes your way for free, why bother? I am sure there are many guys on here who can help with the swap that have done it. You can run an adapter and use your 2004R. Add a shift kit, 700 or 4L60E filter with deep pan and a 10 vane pump, stiffer spring and hardened rings. Your stock stall is decent as is. This is assuming that everything is stock and in good shape. You also have the better 7.625" rear.
I would love to get a LS, but here in Maryland they are hard to find. If someone can on here can get me a LS are point me in the right direction, that would be great. Also sounds like I should be asking you for helping at installing a LS, sounds like you know a lot on it.