351w Waterpump rotation?

It depends on if you use a serpentine belt system or the original "V" belt system. Timing cover depends on if you are going to use a mech fuel pump or electric. Oil pan depends on if you are going to use the oil dip stick in front or on the pan. Balancer depends on belt system you are going to use. Flywheel depends on transmission to be used. Ignition or distributor depends on what you want but if you are running a hyd roller cam you must use a dist. with a steel gear. Alternator depends on belt system again for the type of pully to use.

I currently am running an 87 ford 351W in my 66 Mustang coupe and it uses a reverse rotation waterpump with the March serpentine pully system.

the timing cover will determain if you are going to use a mech fuel pump or an electric. Also if you do not have the rount piece that bolts to the end of the timing gear on the cam then you wouldn't be able to run a mech fuel pump. Some timing chan covers do not have the opening for the mounting of a fuel pump.
If you are going to go to a dizzy i would recomend a msd piece. That being said do not get MSD PN 8584. Because in the future if you want to put a vic jr intake on the car this dizzy will not work with it. You need to get PN 85805. that works with the vic jr intake.
The oil pan i believe should be the same as any oil pan that mounts on a 302 to intall into your car. I would call milidon or moroso and get a 7 quart pan that fits the 351w for your car.
For Flywheel tooth and size we would have to know what tranny you are planning on using. Its going to be a 28 oz flywheel though.
For balancer get a 28oz that is sfi approved. Stay away from the brand name CAT. yes they are cheap.