What is the part number for the stock filter? Is there a larger filter that will fit without clearance problems?

Part no. for the stock filter is PF48 (Ac Delco). GM has done away with a lot of their other sizes. Folks who used to be able to find a longer filter for their cars are now finding that it is no longer made. This may or may not be the case with this filter.

Is PF48 compatible with PF46?

'cause I have a case of UPF44 filters which are a better version of PF46.

There will be some alternate numbers on the side of the box saying what other filters you can use.

Thanks for the info.