I had a 79 Carrera 25ft off shore cruiser. 350 vette Volvo 280 IO. Previously called Crusader, now defunct, Eliminator built a almost identical boat. it would run about 50mph and I could get it airborne using the wakes of bigger boats.
The deep v of the 25ft and longer boats gives a much better ride and a 25 over a 23 is a lot bigger inside. 2- 35 gal tanks.
Ours had a sundeck over the motor so I could stow a lot of stuff in there on each side of the motor and still seat 5 comfortably. Those under the deck love seats are a joke. Trust me, the less seating the less freeloaders you will have.
When the dummies built the boat the installed the motor and outdrive too high. So they had to put a 4in extension on the outdrive (fishing boats have up a 18in extension) and it made it much easier to change the oil.
Our group had 3 of these a 78, my 79 and a 81 or 82. the 81 was built during the slump in the economy and he had less glass then the 78 and 79 and could literally leave us in the dust. So the owner of the 78 rebuilt balanced and bluepinted his engine, blueprinted the carb, took the cup out of the bottom and dished it requiring cavitation plates. We all raced and the 78 and 79 ran neck and neck and the 81 just motored away. Guess who was really pissed.
The sleeks are heavier and therefore a little slower but real nice boats. I personally would not own a open bow.
At that time the volvo, mercruiser IO would only support a 350ci motor, Stern drive would support a bigger motor but their drives were expensive. Some of these old boats now have built 455s in them with the same 280 outdrives the outdrive won't last with those big motors.
IOs are nice, you can steer at slow speeds, unlike jets, they popup if you run over something saving your $100 prop (1980 price). And with the IO directed exhaust are quiet.
Here is one that will probably blow the IO out soon
http://orangecounty.craigslist.org/boa/3049500380.html
If I found a nice boat with a big block in it, I would sell the motor and put a nice 350 ls in it.
A company in FL is selling a ls outboard IIRC ~550hp. Bring a check with 5 digits on it.