You can probably just swap the carb from your 20 to the 18. 18 may be a bit challenged pulling a 60. You could give it a shot and see how it behaves. If it has enough power then leave it alone.
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2264 with 54 GT deck
1641 AKA Black Jack with a 402-E Haban Sickle bar mower
JD317 dump truck
BX2670 with FEL
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