No brake pedal pressure-no brakes
 

Replaced MC (forgot to bench bleed) and a couple of wheel cylinders on a 1964 F250 w/drum brakes. I used a vacuum pump to bleed brakes and the fluid looked pretty good. But there is little to no pressure being built up with the brake pedal. Is it the failure to bleed the brake MC or am I just impatient?

Yep!
Pull it off and bench bleed it.
Then with a helper do the pump3 or 4 times, hold, open bleeder, close bleeder, repeat checking fluid level often.
Dave ----

What Dave said. That'll get you going.

Another major factor is the shoe adjustment. The shoes have to be pretty close to the drum or you'll never get the pressure you should.

You can bench bleed the master on the truck by disconnecting the brake line and running a short hose back to the reservoir. Pump slowly until the air is out then reconnect the brake line. If you are using a vacuum bleeder keep in mind that they will suck air around the bleeder screw. So pull about 2 ounces from each wheel and disregard the bubbles. If you still have a little air gravity bleed them but make sure you don't let the master run dry. I almost always work alone, this is the way I do it and it works every time and takes about an hour.

Re brake shoe adjustment, what I do is adjust the shoes until a hard hand spin of the wheel results in about 1.5 revolutions. You'll need to fine tune that technique, according to your own strength, but it should be in the ball park.