Okay, here is the deal as far as I understand it . . . .
Regular bulbs can be used as parking/brake/turn signals, although heat may be an issue. How Toyota can put fog bulbs in these in the Japanese HiluxSurf's is one unanswered question . . .
LED's CAN be used for EITHER parking lights OR turn signal/brake lights. They will not, however, work as both. Here is my explination as to why, from an earlier post . . . .
Hope this makes sense . . . .
It has to do with the LEDs having such low resistance, and the fact that even though a few LEDs light up for parking lights and a bunch of them light up to make the intensity brighter for brake/turn signal, the wires are connected internally. When the driver's side turn signal is on, a small amount of power will run through the parking light wire coming from the driver's side bulb, back to the light on the passenger side of the truck. With regular bulbs, the resistance inside the passenger bulb is high enough to prevent the light from being turned on. With LEDs, however, because the resistance is so low, it is enough power to overcome the small resistance, making the low power parking light flash on the passenger side of the truck flash in sequence with the driver's side turn signal (higher power). (Enough of the power is used up as it passes through the driver's bulb so that only the few low intensity LED lights come on on the passenger side, and not the higher-resistance high intensity brake/turn signal lights.) The opposite will occur as well, when the passenger's side turn signal is applied.
When the parking lights are on, they of course already have power so the turn signals will not affect them.
If my logic is right, the same thing will occur when the brake lights are applied- BOTH parking lights would light up as well, but of course, you can't see that through the higher brake light intensity anyway. (only a few of the multiple LEDs light up when the parking lights are on, hence the dimmer light, but more light up for the brake/turn signal, hence the brighter light).
Hope this makes some sense.