the thin steel one goes between the b plate & the housing end & the foam gasket goes on the other (outer) side of the plate against the axle retainer. You might fab an L hook with a slide hammer to pull the old seal straight out without nicking any area in the housing ID & HF I believe has a cheapie, not a dealbreaker but a caveat & it is a real good idea to have the plate off of the axle end before pulling it out (& gives you a simpler unobstructed work area there). first measure how far "in" the old seal was so you can drive the new seal inward that same distance. before installing the new seal, clean the housing end & generously swab some sealant around the housing ID at the distance in where the new seal will end up. get a round flat metal thick plate a hair less than the OD of the seal & a drift with flat ends & critical, get the seal started in square with several medium taps then drive it in the rest of the way with fairly hard hits makeing sure it stay square & if it gets tilted just put the drift on the high area of the plate & whack it there easy till it levels out. each whack increases the chances of the seal being distorted so accomplish this with as few strokes as possible within reason. also first put a generous amount of wheel bearing grease on the garter spring on the back side of the seal before starting to drive it in. If you mess up a seal just get another one at your parts house (they're fairly cheap) & this area must be sealed. confirm you have the right seals which ain't an issue from the Doc but parts house items are a different story, just hold the seal in the housing & see if there is just a slight interference. EDIT this is for an 8&3/4, I'm assuming the Dana is the same for this part of it.