as far as i know 70hp only came out with trim \t in 1980 maybe change to a later model transom bracket set up or try & modify & fit 85hp trim \t wich came out in 1976 .
The 1974 trim is a 2 ram unit and the OEM part # was 172670 and there aare several on Ebay but you will have to have the "butterfly " bracket that attaches to midsection for a 3 cylinder to work correctly. OMC Johnson Evinrude Power Trim System 40 45 48 50 55 60 HP | eBay