How about the Lexus GS420 vvti v8, the is300 engine comes direct from the GS and is plug and play, so therefore so should be the v8. Conversion kits are around to marry the BMW 6 speed box to this engine, hey presto.
Incidently I have been watching a GS420 v8 combo on ebay, it's been on a few times in recent weeks (local), coming down in price each time. I saw it relisted for a mere £200 last night, jumped and bit the bullet and pressed buy now , contacted the guy today, it's low milage and can have the complete running car (minus a few bits and bobs) for the buy it now price plus delivery fuel. BARGAIN.
Now maybe a is300 sportcross to put it in lol!
Oh and the Jag looks very well!