The wiring is only part of the problem - more current = more voltage drop so lights probably wont be any brighter - solution relays switch higher current via larger diameter wire.
2nd problem is headlight switch has a thermal circuit breaker internally - more current = more heat so headlights will flash on & off when circuit breaker operates.
Only solution is relays or leave the standard sealed beams.
H4 type headlites will fit into bucket it may be necessary to enlarge the hole in headlight door to clear the rubber boot on rear of light
Sealed beams (or any light bulb) will build up tungsten deposits on the inside of the glass with age and make them dull.
As above, 40 year old wiring, bad grounds and resistance will cause voltage drop and also make them appear yellow.
You will probably find,
with the addition of relays, stock GE or Wagner sealed beams will be a big improvement.
H4 inserts will definitely improve the lighting even more and I think you can get 100w bulbs for the inner high beam.
Again, relays are a must.
Another thing to check, is the spacing of the locating tabs on the back of the reflector is correct.
They may look the same, or close, but some will be "cockeyed" in the bezel
