Actually the "2 oz. for the filter" advice was...
...probably due to the fact that few cars nowadays have 6 quart (as in "Ford V8") oil systems anymore. So, 10 & "two to grow on", maybe?
2 oz. per quart will do the trick, especially if a 2nd treatment is anticipated. My SVX (happens to be 6 quarts!) has over 100K now, but there was really so little 3rd party material in the filter after the initial treatment that I'm going to probably just use 4 oz. per the next three 3K oil & filter changes and see what I find in those filters. That represents years of use on that car.
The F250's 460 will be a little more of a challenge, I'm sure. One of the nice things about this product is there is no time limit as to the effectiveness of the application. If it takes a couple months to accumulate the miles, it will be doing its cleaning while the motor is running as operational temperature is a vital part of the process.
Of course when you are curious about what will be coming out in the oil pan & in the filter it is natural to wish to see those miles run by.
'91 420 SEL @ 199K, '92 SVX @ 181K, '93 SC400 @ 86K, '93 Kaw ZX-11 @ 30K, '87 F250 @ 181K , 2001 Valkyrie Interstate @ 6K, Y2K Honda NightHawk 250 with 1.5K, '88 420SEL I.@ 179K & the 2nd latest, an '88 420SEL II.@ 210K runnin' parts car, '85 F150 300/NP435