You can, but why? Getting your heads rebuilt and doing new chains/guides would be cheaper. Call up VAC, CSS Motorsports, or any local machine shop that does foreign cars and see how much it would be to rebuild the heads. If the chain let go, chances are that the motor shut down well before any other damage was done. If you need new cams, I have a spare set.

Yea I agree. Before you pull the motor. Do a leakdown test after a compression test. See what the damage is like.

the leakdown test is no good, some valves are bent...

i did some cross reference between TUB44 and B46, it seems a few parts are the same... so, maybe, instead of considering downgrading, i just get a used TUB44 engine for donor parts?... I have couple pieces of engine walls busted broken in small chunks of metal...
i still will need fresh gaskets and maybe a few 4.6 specific parts...

stilll looking into it...

The heads are different, just pull them and get them rebuilt.

Rebuilt heads won't help with a broken block.
You may want to speak with VAC Motorsports. I know they can sleeve the blocks. Maybe sleeve a 4.4 block to the 4.6 bore and rebuild from there?
You may check with these guys
http://http://www.data.bmrparts.com/bmwparts/BMW_ENGINE_ASSEMBLY/BMW_11007515721_4.6L_used_long_block.html

While I don't have the 4.6, I do have the 4.4 and was wondering if you were getting the chain slap with cold start ups? If so, how often? In hindsight, should the guides be replaced when we start hearing the brief slap in the mornings?
I've changed the tensioner but it's still happening.

2002 4.4is 132k miles

Absolutely!!! If I knew what these symptoms were, I would have replaced the guides and be done with it...

The block itself is not broken (at least, it does not seem to be a problem at this moment), just couple covers, and they seem to be interchangeable...

Did you look here for an engine?

Used and Rebuilt BMW Engines For sale -- BMW Engine Ready to Ship

You sure its bent the valves?? Mine did the same thing at 70mph and I had to drive it about 2 miles with a hell breaking loose under the bonnet to get to a pull over. Cam chain bits were not happy, but no damage anywhere else (at that time anyway). I would pull it out and strip it first. Its got to come out no matter what you decide to do, and taking it apart is cheap. If you do it yourself putting it together should cost no more than 3000 of your American dollars. You might get away with a cam cover, chain and guides

Yo Terminator,

What's going on with your motor? Hope you are getting more good news than bad.