The up to date answer is, as stated in other posts, you can convert the engine to full FLOW oil filtration at the time of rebuild by following the instructions in the tech tip.
Without modification you can only use a 'bypass filter' which, unlike full flow filtration, only filters about 10% of the oil.
The shortest answer to your question is:
Yes, you can add a bypass filter without modfying the engine. (this is what Grigg already said).
'51 Chevy 1/2 ton w/'62 261, HEI, offy, fentons, dual carter/webbers, t-5 & 12 bolt posi
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