Marvel Mystery Oil, how much to use

98 4.0 128k, gots a nice knock on cold startup, im thinkin its a sticky lifter, already checked flexplate and its fine, i was just wondering if useing 5 qts 10W30 and a quart of MMO will be ok, have a 800mile round trip coming up in 2 weeks and dont want any problems

Thats the amount I always use. 1 QT per oil change, so in this case 5 QTS oil/1 QT MMO.
Don't expect an instant cure, MMO is a mild product,if sludge and varnish are not very bad you may get it one treatment, otherwise it may take a couple/few changes.
Don't forget you can add it to your gas too. I forget the exact amount but it's on the container, I use it my tank too.
I'm not a believer of "mechanic in a can" but I would have to say IMHO this is a time proved product, been around since I was kid (ya.. we used it on the Mayflower coming over from England...lol). I remember my father using and I've used MANY times growing up on engines that seemed seized to ones that had lifters so gummed up that max speed out of 455ci eng. was 35mph, took a few treatments but that eng purred when done.