Looks like just a casting difference. Your port looks much "shallower" than the 862 port does hence why the valve guide is taller on the 862 prob. Did you put those machining marks below the guide? cus that looks restrictive as hell!

Not sure why there is such a drastic change between the ports... maybe has something to do with the chamber design/sizing. I know the 862s are the same as the other LS1 5.7 heads besides the chamber volume and intake valve size. WHich causes the restriction compared to the 5.7 heads but otherwise the heads flow the same... once the intake valve has been upgraded to the 2.0".

 

I think the mark is from when the factory cut for the valve seat inserts. I just now checked my sacrificial 241. The valve guide looks like yours...raised up a little. It must just be a difference between 243's and the others we are looking at.