Pretty sure he is already 12v there aren''t many 6v winches and I think his 153 in a Chevy 4 that came out in '62
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There are two styles of deep cycle marine one is really a dual purpose that does a pretty good job of cranking and powering moderate loads over a longer time. Read the description and get the most powerful battery that can fit in your space. Also use the largest cables you can afford from the battery to the winch. DC loses a lot if cables are too small.
Although the higher output alternator will draw more power from your engine when it is putting out it's maximum amps when will that be? It should act pretty normal with your regular light loads and just keeping the battery topped off. It won't normally put out 140-200 amps unless the loads are drawing the battery down. At times when it may be assisting the battery run the winch you probably won't be using the engine to move the jeep so the full 90 hp can run the alternator. I have a big Miller welder that came with a 4 cylinder Jeep flathead four. The welder can be used as a 10KW power plant plus another 1100 watt auxiliary generator. No where near the 90 hp of your 153. I think you would be fine with a 75-100 amp alternator. On a long hard pull you might want to give the winch a break and let the battery charge a few minutes.
