oil filter conversion

[05gt]

my 57' has the 312 V8 with the canister type oil filter. I bought the conversion for it to make it use spin on type filters. My question is, after I pull off the canister, do I have to pull off the old adapter plate and install the new one, or do I put the new assembly over the old adapter plate. What I'm running into is, the new oil feeding screw that you mount the filter to fits in the filter ok, but the other side of the screw that mounts everything to the block is to big. I see that the canister has a plate also on the side of the block, But I'm not sure if it stays on, or does it just pull off/ twist off? Any help as always is greatly appreciated!!!

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