Great boat, well built but at 465hp out of 426cid these detroits are well over the common sense hp/displacement ratio. 1400 hours and 27 years means they may soon need a rebuild deoending on how they be been used
First thing to do before a survey is cold start and check the initial smoke, engines need to be dead cold as in not having been started in 18 hours. A puff a grey smoke is ok but it should clear quickly and they should settle into a smooth idle right away, any lasting smoke, any unburned fuel on the water or any hunting around before reaching steady idle woudl be a red flag.
On the plus side, these boats are worth spending money on...