I'd guess you've bent a valve or two. That's why the pulleys are tight, the clearances have gone on the rockers.
When the head is off, check the valve guides as they are known for splitting.
Check also the conrod play. There will be some side to side and possibly even a little "rock" but you don't want any radial movement.
I've got a couple of 748 head s lying around if there is a lot of damage
