
Good question and one that is in my head in a daily basis..

Start with either a stock (unmodded if you can find one) 1971 Marshall MK II 50 watt big box head, the big box is very important

My choice would be George's MK II '71 spec clone, which he has already made a few, this is the BEST choice!! Send your YJM308 pedal to AnalogMan Mike, have him do the Mojo 741 op amp mod, which returns it to grey DOD250 spec, then get a Boss NS-2 Noise suppressor, very important and not tone sucking as some will say, then as far as speakers, Yngwie always says he uses the G12-75 watt speakers as he wants power tube breakup, but not speaker breakup, with his front end boosted signal.
I believe as far as recording, in his home 308 studio, I have seen pictures of basketweave cabs and there is no reason to not assume they are original 30H's, this is a grey area, a lot of Yngwie's mystique is based around,"what exactly is he using??" There are some great guys on yngwie.org/forum, especially Deuterium who has recently 'crossed over' to here, but there is as much misinformation around Yngwie's equipment as good information.
I have been meticulously been studying everything Malmsteen for the last 4 years and have heard or read it all, I am somehat of a scholarly type when it comes to equipment details, but learn new things everyday!
As far as live when I saw him Nov 2005 in Tucson, he was using two stacks, one 'wet' or carrying the effected signal and the other dry, closer to him, as far as all the other gazillion amps and cabs, I know they turn on and off certain 4X12"s to give him a guitar monitor signal wherever he may be on stage. Even on stage right where the bassist and keyboards always are, he has his guitar stacks as well, a lot for effect, but the two or three live stacks, miked up seem to be his main rig. He uses 100 watt heads live as well as the 50 watters.
He is using a grey 250, here is a shot of the front of the stage showing the old Roland DC 10 echo that he uses at the end to speed up the repeats as he either throws the guitar in the air or smashes it, either one

http://i57.photobucket.com/albums/g219/" onclick="window.open(this.href);return false; ... 0e40ea.jpg
Here is oder link, he dosent use the same bass pedal setup as this now, but as all my shit has been deleted, I can't find anything to give you the definitive answers that i once had

http://www.guitarraonline.com.ar/set%20yngwie.htm" onclick="window.open(this.href);return false;
http://guitargeek.com/rigview/259/" onclick="window.open(this.href);return false;
http://www.bossus.com/bugonline/feature" onclick="window.open(this.href);return false; ... =malmsteen
http://www.bossus.com/bugonline/feature" onclick="window.open(this.href);return false; ... msteen_rig
Notice it says his amp EQ is bass=2, middle=5, treble=6. In the floor pedal board he has the old grey DOD250 overdrive. This must have been before the YJM308 came out.
I just used Google to translate the page into English for you. The wording is a little screwy but you can make sense of it:
Picture 1: This pedalera has two rows more than the one than the guitarist used in previous years. These two rows control the effects of delays Korg and the TC Electronics. Malmsteen has in addition wah here wah CryBaby chromed Multi-Wah CB-525 and a pedalera to low that shoots to cords low Mellotron type or type Moog Taurus of the Vintage Keys of his rack. With respect to delay analogical that is on the pedalera, one is a Korg of the '78
Picture 2: Rack of 1998 includes a wireless system Samson and DL-3000 of Korg. In addition a Furman Power Conditioner contains, the module Vintage Keys, delay DL-3000 of Korg (x2), rack TC Electronics and the control of control Audio Custom Electronics of the pedalera. The effect pedals are: DOD 250 (preamp-overdrive), Boss OC-2 (octavador), two Boss NS-2 (sound suppressors), Boss BF-2 (to flanger) and a Tube Screamer de Ibanez (overdrive).
Picture 3: Live, for more than twenty years that the guitarist uses the Marshall. 50 mall pillows of watts MkII without masters with speakers JCM 900 of 4 12 xs