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I got one at the dealership but it's a discontinued part now.
Used might be hit or miss.
The 6 hole Magnum won't work on a LA block.
NOS
NOS Mopar 1956-1992 Plymouth Dodge 273 318 340 360 Oil Filter Adapter Plate | eBay
Billet
Canton Racing Products 22-575 Billet Aluminum Filter Plate | eBay
You can use the fitting out of your 90 adapter.