When you say the fan touches the harmonic balancer I'm not sure how much. If it hits the pulleys you've got something to deal with, if it is 1/8th of an inch or less you could tweak it. up to a 1/4 or 3/8 you could probably get another spacer.
'54 is when the new longer 235 was introduced w/full pressure oiling and insert bearings, by 55 all the 235's were the newer ones. So if the truck is 551st or later there shouldn't be a length problem with a 235. If you've got a pre-'54 235 the problem would be that it is furhter from the radiator 'cause its shorter.
To figure out the year of the engine you'll need the numbers on the passangerside of the block near the starter.
'51 Chevy 1/2 ton w/'62 261, HEI, offy, fentons, dual carter/webbers, t-5 & 12 bolt posi
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