The gear.dk converter can drive the speedometer, I believe:
SpeedoOut
Also, as far as I can tell (I may well be wrong!), the output flanges are removable from all types of 722.x gearboxes (Just a large nut holding it in place onto a splined output shaft), so judging by any lack of mention of need to modify a prop shaft in any of the online info from ofgear.dk - I'm guessing the output flanges may be interchangeable.
...Anybody actually done a conversion like this yet, who could shed light on this?
So I spent some time yesterday evening looking at the other necessary hardware that I'd need to do a conversion such as this to get an idea of costs:
(1).
WEB-Shop (Cost 674 Euros + Postage to Japan. VAT not payable as outside the EU. Kit from Gear.dk. Boost control needed??).
(2).
WEB-Shop (Cost 120 Euros + Postage to Japan. VAT not payable as outside the EU. Kit from Gear.dk for OM603 Throttle Position Sensor).
(2).
A804 W203 C55T AMG 5AT ミッション ★59280Km ★... - ヤフオク! (Cost 83,160 Yen + Shipping. Used low mileage 722.636 transmission from 2005 C55 AMG. Has more friction plates than others, so this would be a better choice than cheaper but older low mileage 622.6 transmissions).
(3). Oil cooler lines & small cooler (Cost estimated at 25,000 Yen).
(4).
メルセデスベンツ純正オートマオイル★ATF 722.6... - ヤフオク! (6L MB ATF Fluid - Cost 16,200 Yen incl. shipping. Transmission Oil).
(5).
★激安即決!!★☆ベンツ ATF 722.6 5速用 オイルフ... - ヤフオク! (Cost: 3,670 Yen incl. shipping. ATF Filter, Gasket & Postage for 622.6).
(6).
【M's】AMG W209 W203 R171 純正品 パドルシフト... - ヤフオク! (Cost: 26,211 Yen incl. shipping. AMG Paddle Shift Lever Set).
(7).
W210ベンツE55AMGワゴン☆シフトゲート/ノブ☆B9... - ヤフオク! (Cost: 10,800 Yen excl. shipping. W210 shift Selector assembly).
(8). For switching the 622.3 OM603 compatible bellhousing onto the 622.6 gearbox: Bellhousing steel gasket MB Part number 1402774214 (Price unknown).
(9). Used Steering wheel with 4 rings on the contact wheel, in order to run the paddleshift buttons (Could do this job later; wouldn't have to be done same time as the transmission swap).
I think that about covers all the anticipated costs (Would cost me the equivalent of around £2,000 to do give or take a few bob), unless I've missed something else?