For me, I wouldn’t change anything. That .072 OD on that box with your tire size will give you about 2800 rpm at 75 MPH. If 2800 rpm is too high for you, you can drop down to a 3.91 and at 75 MPH you’ll be at a bit over 2600 so you’d gain a couple hundred rpm.
Im usually no more than a couple of weeks out. The exception is going to be when my engine goes on the pump. It will stay on there as long as it takes for me to flog its guts out.
I can’t imagine it would take me more than three days to break in the cam, install the inner springs, retorque the heads and finish the break in and then break in the pistons.
After that it will be sorting out the timing curve, tuning the carbs, adjusting the headers and lash loops. If all that goes well it will be about three days.
I try not to get myself buried because physically I can’t do it.