Borgeson Power Steering Thoughts....

Anyone out there that could recommend a 20:1 vs 24:1 steering box for someone that isn’t getting any younger? Secondly - who might I contact to make sure I purchase the correct steering box for a 1971 Duster with a 318 and manual steering (manual everything)? If it makes any difference - the car was built in June of ‘71 (almost at the end of the production run). I’ve come across a part somewhere that matched a 72 Duster rather than a 71.