PYE model i.d. please!

[ppppenguin]

Rather than using a relatively scarce AD149 I think I'd use modern silicon. If you're moving away from the original design then authenticity isn't really relevant. Either a PNP power device such as a MJ2955 or a 3A rated variable regulator chip should work. Both of these are a lot tougher than an AD149 too. The bypass resistor is a good trick for minimiing dissipation in the device, provided you can ensure that the load will always be present.

If running from already stable 12V supply there's a good case for dropping to 10V using a string of 3A rectifier diodes.