I have at least 15 BAR Mags- they probably need to be refinished...The Valmet was available in .30-'06 with a standard-length receiver. So was the Saiga.
The only detailed description I've encountered was of the Saiga, done by "BattleRifleG3" on forum.saiga-12.com, Feb 2007.
Pictorial Writeup: Saiga-100 in 30-06 - forum.Saiga-12.com
* the magazine well is moved back from the standard position
* the center support is moved back
* the hammer is notched to clear the relocated center support
* the barrel is moved forward in the trunnion
* the bolt face is moved forward in relation to the locking lugs
* the .30-'06 bolt appears to be the same as the .308 Saiga bolt
* the picture in his post is small, but the bolt appears to have the third lug like later .308s
A Saiga magazine isn't much use in a standard AK. Valmet '06 magazines appear to go for $100-ish. One of the magazines below might be adapted, perhaps with a magwell extension attached to the bottom of the receiver:
Johnson LMG 20 rd ($62 on GB)
Browning BAR 20 rd ($40 on GB)
FN-49 10 rd ($50 on GB)
The snag is "first you get a .308 Saiga bolt". Since they're basically unobtainium, the simplest solution is to adapt a standard bolt. The main difference is the Saiga bolt is longer from the locking lugs to the bolt face. This could be easily handled by cutting off a spare bolt, turning it to spigot into the original bolt. Braze or silver solder as needed. By cutting an extra bolt you would avoid having to make all the cuts for the extractor. You'd need a longer firing pin; cut and weld, or perhaps a PSL pin.
The ejector would have to be moved back. I've seen blank rails, or you could cut and weld a left rail to move the prong back.
The bolt carrier travel is more than adequate to handle all this.
The front of the trigger guard and the mag latch would need to be moved back, or just bend up a new one from scratch. The latch would depend on which magazine you picked, and whether you used a magwell extension.
reference for pressures: (Wikipedia, in CUP)
.308 Win 62,000
8mm Mauser 57,000
The .30-'06 should be safe with a standard AK trunnion.