I have used the Ryco filter for the magna on my '75 (Z456) and it has been fine.

Sump plug and gasket I just went to my local Auto One store and gave them the vin. The magna sump plug works just fine, the genuine 380 sump plug has a deeper head and from memory uses a 14mm socket instead of the magna one which uses an imperial one iirc 9/16s I think.