Can anyone here tell me (Comp Cams Can't) if the installed height of the 918 Comp cams spring is different with the 787 retainer vs the 774 retainer on a vortec head?

I originally ordered the 774 retainer to use but they are for use with LS1 valves and my installed height was 1.7 rather than the 1.8 I need, so I have returned them, for the 787 retainer for use with the non-LS1 valve. However, I would like to find out (if possible) if there is any difference in the installed height so I know if I'll need to order +.100 longer valves or not.

FYI I'm setting up the vortecs to run with the 268 XFI cam with lifts of .570 and .565, any info anyone can give that may have done this set-up or something similar with the vortec heads is appreciated.

Rob