Brakes - questions

[53lowdown]

62 C10 with ~ '70 front discs, stock rear drums. Dual Master from 68 Impala disc/drum, and 9 inch aftermarket booster.

I can't get this thing to stop quickly - can't even lock up the wheels on wet pavement, so a panic stop would be a real panic.

1. The Booster seems to be working - Hold pressure on the brake peddle, then start engine and it pulls the peddle down.
2. Pads look fine - hardly worn
3. I've bled the brakes 3 times - and I'm not seeing any bubbles.
4. It stops straight - no pulling to either side

The peddle seems a little mushy but it doesn't keep going down.
Pumping the brake peddle makes only a minor difference.

I was thinking maybe replace the front hydraulic hoses? But fluid seems to be flowing well when the bleeder is open.

Would a bigger booster solve the problem? Seems like even with no booster I should be able to lock them up if I stand on them hard enough.

Any other ideas?