Master Cylinder?

You should bench bleed the new one before installing.

Get some steel brake line with the correct fittings (or adapters) to thread into the master. Cut short lengths and make 'em up so they loop up and into the reservoirs, near the bottom (they should extend at least halfway down). Clamp the thing in a vise, being sure that it's perfectly level. Fill with fluid, and use a plunger of some kind (maybe a large screwdriver) to work the piston. Bubbles will be forced through the lines and released through the fluid in the reservoirs. Repeat until there are no more bubbles.

Do not push fast, and don't just keep pumping like a mechanical tester. You don't want to suck the bubbles back in, and you don't want to foam the fluid. One slow stroke and release, let things settle for half a minute on so, then another stroke ...

New/reman masters usually come with a bleeder kit, check for one first unless you want to fashion one like Eagle suggested. When you clamp the new one in the vise, DON'T clamp it from the bottom side where the piston is (it seems like a logical place to clamp at). Instead, clamp it at the flange end where it mates to the booster...don't overtighten the vise, just enough to hold it (level) while you push the plunger in. You can tap the bottom of the master while you have the plunger in to help persuade the air bubbles out. Don't press the plunger in too far (about 1" max) or you could fubar the rear seal.
HTH,
Jeff

Not too bad of a job, but yes, you'll have to push the air thru the system out thru the calipers/wheel cylinders that you get from where you discoed the lines at the MC (unless somebody knows another way?). It's a good exercise anyhow, completely flushing out all the old fluid in the system. When you get the master bench bled, cap off the ports and put the cover back on it and reattach it to the booster. Thread the brake line fittings back into it until snug but not completely tight and put the wrenches on the fittings so they're ready to do the final tightening. Have someone slowly depress the brake pedal (but not to the floor) while you tighten up the fittings, then release the pedal. Have a rag under/around the fittings to catch the fluid that'll squirt out when you do this, BTW. That way, you don't end up sucking air back into the master and have to re-bleed it. Then go ahead and bleed them as normal. Also, a good set of flare nut wrenches is a wise investment so you don't mung up the fittings...they're different sizes too, the one in the front's 1/2" and the rear is 3/8" if I remember correctly.
Jeff

The only thing I will add is to not use a "good" screwdriver to work the plunger. You don't want to score the thing. I took an old #2 phillips and ground the end to a fairly smooth ball to mimic the rod in the vehicle. Less danger of damaging what you're trying to fix!

There’s no need to take it to a shop to have it vacuum bled. A Mighty Vac is $40 at Sears and works like a champ. I imagine that’s about what you would have to pay a shop to do it. This way at least you get a tool for your money. The little Vac has a gage on it and works pretty well for checking brake boosters and intake manifolds too. When I converted my ABS to non-ABS I installed speed bleeders and used the Vac to get all of the air out. It’s not hard to do, just a little time consuming.

I just bought a new MC from Autozone and it came with instruction to bench blead.

Bronco said:

Just thinking nutty here. Bear with me. Could you run some tube from each of the 4 wheel bleed screws back to the MC and just pump the brakes till they clear all the air? It would be a lot of tube but seems like it would really let you go to town bleeding it. I’m putting it in tonight and I don’t have that much tube so I’ll let you know how it goes. Thanks for all the help.

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The biggest problem with this approach is that you are recycling dirty, contaminated, old brake fluid back to the MC when you do this. That's not a good practice for long healthy brake system life.

The swap went just fine. It wasn’t hard at all. I got a bench bleeder kit from NAPA with the MC and the thing when in about two hours including bleeding. I think it could still use another round of bleeding. I just did it the old fashion way. The only problem I ran into was that one of the bleed nipples was clogged so as I tried to loosen it to get it to bleed I had to go to far and it started coming out the threads. I ended up pulling it all the way out and picking/blowing the crud out and them having to start over bleeding. Big mess and a PITA but no big deal. Thanks for all the good tips it really made the job go smooth.