Louis,
Don't trust the Chilton manuals. The 455 in the GP was 370 HP with 500 lb ft of torque. The true HO disappeared entirely in '70. The only cars (in '70) with anything like the HO manifolds, HO cam, etc. were RA III & RA IV F and A bodies (Firebirds and Lemans/GTOs). The '70 455 is still a great engine. It was the only year the 455s came with high compression. The engine was very similar to the 370 HP 428 from 1969, just torquier.
There were about 65,000 GPs made in 1970, and about 1/4 of them were model SJ's.
If it is in pretty good condition, I'd buy it if had the opportunity.
Good Luck,
K.
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K
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