It is typical with Indy heads to see folks turning less than the combo can do or likes--I mean--I see on the dyno all the time when ports are borderline big or just plain too big to make peak power at a reasonable rpm like 6500--we see combos with dash ones all the time that keep making HP way past 7500-7800 range --that is out of the comfortt zone for most racers and really they should build combos for lower power bands as bracket racers just so it ain't so darn hard on everything--hard to get folks to size the port to the unit correctly and not over cam but that is the way the world is so....
I am saying that lots of guys can turn that big cube engine another 1500--1800 RPM and really see what they got! Too scared to--and rightly so. I hate the myth about big cube loves low ROM yadda yadda--Na--they LOVE to have the crap turned out of them usually to make impressive peak numbers--just like ANY good race engine
Jr Johnson said it best--Give me an engine that never quits going upstairs and let me do the driving. He was right.
The old Shift Loop is long forgotton but PLENTY useful tool --use it to discover what your combo Really likes--Many times just buzzing an engine another 1000 RPM is the key--
Go get him!! Good Luck!