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If ypu want to find the hull id # I would try sanding carefully in the bow locker. On my 1966 the number was on the vertical wall of the locker towards the stern of the boat about 2" up from the bottom of the well.
The numbers are white so it may be very tough as your interior is white.
Console, I would go after market fiber glass unless you want the traditional look. Motor I would recommend is 70 HP.
Yamaha makes a 4-stroke that is not too heavy, I have never owned one but like my 115 HP 4-stroke. If you are a speed demon, or carry lots of people, a 90HP may be better but I have a 90HP on my 1966 and it is truly scarey fast. My kids run the boats and are adults, but let one person at the throttle that does not get it and it would be less safe than I would want.
The 70 HP on the 1964 is plenty in my opinion.

Rails are as Phil mentioned. I like the side rails toward the middle/stern, but have removed from the 1964. I will not put them back, but have kept on the 1966. The bow rails are in my opinion stupid and if I owned a Whaler with them I would remove at once.

Hull looks great, as said earlier it is a great place to start. Clean platform.