100 watt 12 volt headlamps will pull 8.5 amps each on high beam, for a total of 17 amps. If your H4 lamps are DOT approved they are probably 65 watts and will pull about 6 amps each, 12 total. A single 40/30 amp cube relay for low beam and another for high beam will handle the lamps well.
You will find a lot of these relays will be rated at 40 amps on the normally open contact (pin 87, the one you'll be using) and 30 amps on the normally closed contact (pin 87a which you won't use).
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12
'52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
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