All single engine Y Block boats I have come across were reverse rotation. It either has to do with an over abundance of reverse rotation drives/props and it was probably cheaper to reverse the motor rotation than to buy a new drive who knows? Maybe the companies building the boats got a super deal on reverse rotation drives in order to use them up? There must be somebody in the boat bussiness that knows the reason.

I was not aware of the differnces in the cams (Teach me to listen to unconfirmed sources)  

55 Vicky & customline

58 Rack Dump, 55 F350 yard truck, 57 F100

59 & 61 P 400's, 58 F100 custom cab, 69 F100, 79 F150, 82 F600 ramp truck, 90 mustang conv 7 up, 94 Mustang, Should I continue?

just had access to web site re dual engine instalations. ther quote is counter rotating props a must for neutralizing propellor torqe which dramaticle improves vesel handeling and performance.Aded to makes vesel easeyer to dock and turn..Aswell as propes turning port cw starboard ccw lifts the stern . props turning port ccw starb.cw. lifts the bow.
  could find no info on single engines being ccw frome the front being aney advantage.or reason other than prev.coments
 have a reletive who ownes a 45ft pleasure craft with 2 c9cats rated at 500hp each  driven threw twin disc gears( 1 runs reverse other forwerd) to give the counter cw and ccw rotating props.controles work as if bothe ar forwerd in the forwerd position.

Ya know...thinking about this in that aspect, wouldn't it also make sense that to stabilize the single engine torque rotation that if you reverse the engine from the prop, you then would also even out the torque twist from a big engine in a relatively small watercraft? This makes sense.
Anyway, what trans combination would be best for a F.E.D. with this engine and a radical cam, headwork, etc...???

ther ar maney choices for gears. if you ar useing a vdrive prop shaft would turn oposit engine, if you use a center mount engine witha simple forwerd reverse boxb warners can be set for ether rotation. reduction gear you  will have a choice of rotation, (on modern) gears. if looking for a gear ,i would consult a marine dealer for best results.

I am not putting it back into a boat. I was thinking about installing a clutch in front of the Velvet Drive and using it to power a nostalgia front engine dragster.