This has been discussed lots in the past .I filled a clam up to check its capacity ,it takes just one pint, but you do not want it completely full .If your seals are bad in the rear and axles you will get the level increasing .in the rear , These Uni joints lasted a long time in the past but were abused particly when high melt greases came along . When the mechanic did the 6 monthly grease up he put a few shots of grease in the Un zerk/Nipple this tended to seal the inside and reduced dripping from the claim ,then he topped up the tranz fluid .You will notice the tranz and motor slope back on a flathead so you got some spill over into the Uni joint this all mixed to gether and got the thing lubricated .I think the closest to Ford Soda soap Un grease now days is CV joint grease from a modern front wheel drive car some use Corn head, I used a home brew mix .Don't forget the front drive shaft bearing ,very important to have that lubed.