Hello Thomas, I've owner manual (67/74 Haynes) but nothing about automatic gearbox... the most important for me is to choose the good oil and take care of my gearbox... I know there are tunnings but it's me first automatic so .... learning before doing would be better....
From what this says Ford ATF seems to be the favourite - and to avoid fluid with the Dexron additive as that doesn't work well with the original asbestos brake bands.
Can't find it in my factory workshop manual either but the parts book for '71 and '72 models does list the automatic gearbox with auxilaries, so I'll have a look in my grand dad's workshop manual as mine is a '69 manual I believe and my grand dad's might be a later one.. Will let you know as soon as possible...
'68 sunbeam rapier fastback {B341006846 OD/LHO} I like a car that looks normal but really knocks your socks off!!