CSL needs a new block - advice needed

[ithinkihaveone]

Hi all, I recently bought a CSL and it wasn't a good one (not long out of the hands of a prolific CSL seller on here with his service stamp so I thought it would be good). In the end, it's my fault for buying it. But now I've got it and I'm going to get it sorted.

The head was loose and it's knackered the head gasket but also damaged the block. I've had the head skimmed and the mechanic says I could take a bit off the block, fit a new head gasket and it'd probably be OK but I want to do a proper job and rebuild the motor, so it's as good as new. So I'm opting for a block from a low-mileage motor, new piston rings and it should be good to go.

A few questions:

1) Is the block exactly the same as the standard E46 M3, down to the part numbers and markings on the block itself?

2) Is there anywhere you'd recommend to source a decent block?

3) If you had to have your engine apart, what other parts would you look at replacing while you're there?

4) Are the standard head studs OK or should I get uprated ones?

5) Is the standard BMW head gasket good enough or should I uprate that too?

6) Have I missed anything?

Thanks in advance.