I bought a new master cylinder for my 70 Dart and the push rod seal did not come with it and the parts store did not sell or get one. I called Mancini and there out of stock. They will get more in a few weeks. The part is only 3.95 but they said shipping is way more then that. Does anyone know were to get one. Someone said they used a piece of hose. Does that sound like it would work if so what kind of hose and what size. Thanks for your help.

Your master cylinder has a spot for one right?
PM me your address and I'll send you one.

Are you talking about the dust boot, or the retainer (shown above)?

At your parts house get a snip of vac hose the same length as the recess behind the rounded nub on the end of the pushrod. I forget the dia but just hand the guy the pushrod & have him cut a piece of a dia that is tight over the nub. The OE retainer piece is identical to a snip of hose except it has a groove along it's length which might be there just from the manufacturing process or put there deliberately to let air excape when you push it into the blind piston recess so it will seat all the way so I cut a shallow groove just to make sure. Look in the back of the M/C piston & if the recess is smooth tapered like the inside of a thimble then it is a power brake M/C & will not work in a manual brake app. If the inside has a wide machined groove around the circumference about halfway down (that's where the retainer hose snip seats) then that is a manual brake M/C & you're set (assuming the bore dia is what you need for your setup) though I used a 1&1/8" bore M/C in a manual brake app (74 A discs/10" drums) & the pedal was not excessive

Actually a manual brake M/C must have the machined groove for the retainer though a PB M/C may or may not have it as the snip of hose ain't used in a PB app therefore the recess is not used & if it (the recess) is there it serves no purpose other than the M/C can fit both apps assuming the bore dia is correct (or close enough)

I just wanted to clear that up. I just recently bought my master. I was looking for one with 15/16 bore. The manual one at O-Reilly didn't have it (it was larger), but the Power one did. They both had retainer recesses, so they could both be used in manual applications. You just gotta look before you buy that's all. Don't assume a power master won't have a recess. They all seem to be different depending on the manufacturer.