Main Bearing Shells

I have recently purchased a secondhand engine for my sons Fireblade, the engine was bought knowing it had a main bearing failure( after 7000 miles).After pulling the bottom end apart we could clearly see the second from alternator side main had spun my question is do i replace them all whilst its apart or just replace the one which has spun, i have already purchased a full set of shells. My thoughts are that the bearings which are already fitted are bedded in now and fitting new bearing shells will require the motor will have to be run in again. Torn between the two options, suggestions/opinions please.

 

Replace all of them while the engine is apart, if you replace only one it'll need bedding in.

 

as above

 

Replace the lot!

False economy to only replace 1

 

I would be looking at why it spun a bearing at such low milage?
Is there any other engine damage if it has been starved of oil?
Is the crank round or has it's journal gone oval which caused the bearing failure due to heat?

 

i,d change them all!!!

 

Thanks to all, the original intention was to replace them all hence buying the full set. But when looking at the bearings with no damage thoughts got a bit muddled.PeterT, Will check the crank journal tomorrow for out of round.