I recently did a full alignment and shaft re-build on a 1968 115' feadship with two cooper bearings on each side of a 30' shaft run. They are great bearings, very simple design and have been in use for a long time in a variety of applications.
With a full re-power and re-design of your drive shaft arrangement, I recommend you contract a maritime engineer/architect to spec up an arrangement. I cannot stress how important all components from the reduction gears to the prop are to the performance, safety and quietness of the ride. Drive line components and engineering have come a long way since the "old days" and there are a lot of options to take advantage of (vulcan couplings, thrust bearings, dripless shaft seals, hydraulic couplers, composite bearings, etc.). A few things to note on Cooper bearings:
1. I am not sure of your mounting specifics for the bearings, however, I assume they will be mounted to plumb frames or bulkheads. Note what your shaft run out angle is in relation to the mounting surface. Cooper bearings only allow for 10 degrees of play from center. If you shaft run out is greater than 10 deg in relation to your bearing mounting surfaces, you will need to create an appropriately shimmed surface.
2. Be sure to re-set the bearings once you are back in the water as the vessel, (which I assume is >50M with 8" shafts) will settle and sit differently in the water. The cooper bearings gaul very easily when there is misalignment. In the same manner, be very adamant that you check tolerances on your cutlass bearings often for irregular wear. Once they begin to wear the load is distributed unevenly on your cooper bearings, causing galling. Once they are galled, they will chatter and "growl"...eventually self destructing.
3. Install satellite grease points and grease often.
PM me if you have any specific questions. The coopers are great straightforward bearings. If you haven't already, contract a qualified professional to spec. out the arrangement for yourself.