I have a a set of 853 that have been ported, 3 angle valve job 2.02/1.60 ss valves, they flow around 300cfm, comp 918 springs .625 lift.. I had them on my 2000 silverado full weight on a stock spec 5.7 bottom end with a 228/230 comp cam and went 8.0 in the 1/8 motor and 7.22 on n2o spinning.. $700 obo
5.3 came out of tahoe runs great had it in my truck while i built my 5.7, long block never been disassembled... $600