Rear axle volvo amazon question

Hi. I wondered if someone can give me a bit of advice please. I have a 1965 amazon, which we are currently building to race. I understand that the rear axle is a weak point with the amazon and i have been given different advice. I have been told that as it is a safety issue you can replace with an axle including rear brakes (was changed to discs from drums) from a car after 1966 when they were improved in period. However, would this be acceptable under appendix k? If not it seems quite a bit of work to improve the original axle. Thanks Mark