Originally Posted by Mr. Sandog

I'm no engine wiz, but if the 4.8 and 5.3 have the same bore but different stroke, doesn't that mean different cranks?

Originally Posted by mcfarlnd

you also have to remember, if you go to "iron block", its gonna be a fresh brand new motor which is a nice piece of mind. you never know what happened to that "5,000 mile 6.0" you get from the local junk yard or how hard it was driven or even if it has low miles as stated . you can put together an iron block 5.7 short block for fairly cheap, all you really need is stock ls1 pistons, 5.3 or 5.7 crank. punch the block out to 3.898, fresh bearings and rings. then whatever else you want to replace such as cam, timing chain, lifters and trays etc... and some people might disagree but, 4.00 isnt all that much of a difference from a 3.898. i think its more of a preference or someones budget will sway them in the direction they want to go.