I just went out to the garage and measured a bare 360 block I have and 7-1/2" is just right.
Also to respond to the worn lifter bores. It can cause lower than normal oil pressure. I know because the 360 in my Cuda now is like this. The lifter bores measure from .9058-.9067. The book calls for a max of .9055 so it's out of tollerance on all lifter bores. It does have lower than normal oil pressure but not that much. It starts at 65 psi cold then when it's fully warmed up drops to 30 in gear idling and goes right back up to 55 when you hit the gas. That's with 10w40 oil.