The original owner's manual from my 87 GN says the following:
"We recommend that you limit your speed during the first 500 miles to a maximum of 55 mph but do not drive for long periods at a constant speed, either fast or slow. During this time, avoid full throttle starts and, if possible, avoid hard stops especially during the first 200 miles of driving.
Always drive at moderate speed until engine has warmed up."
For what that is worth, not sure how that applies to a rebuild...I know you are supposed to change the oil after only a few hunded miles.