I thought you always needed at least a 400 TH. for any Big Block, but I put a (425 HP.) 454 in my 79 4x4 pickup with a (new re-built)350 Turbo,and hauled a 24 ft Camper with 2-4 wheelers in back ,I pulled some 6 % grades in Wyoming with it & never had a problem,.
Just put a shift kit in it, and a good cooler on it to keep heat down,I also used one of the oversized ( 2 extra qt.)pans with the cooling holes in it( remember heat Kills!).
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