On my 1950 two-ton 6400 I’ve rebuilt and installed a 1954 261 engine. The dipstick goes all the way in and actually hits the bottom of the oil pan. Yep, she’s in all the way. On the dipstick is a little metal disk that covers the tube when the stick is in. About half way up the shaft is a little notch area that looks like the metal disk cover might used to have been tack welded. Is your little tube cover attached to the dipstick or does the cover freely slide up and down the dipstick shaft? Does your dipstick bottom out in the pan? With the dipstick bottomed in the pan, 5 quarts oil looks to be a qt too full.
I’ve not taken measurements to check dipstick depth as have nothing to compare them to. Could measure how far the stick’s notch drops into the tube when the stick is bottomed out and how far the notch goes into the tube, bottom of pan to top of the tube, etc.
