Interesting. My POH specifically calls out the E-3450. And, the new filter appears to fit significantly better than the old one, which had shrunk quite a bit. The old filter was barely (or wasn't) sealing against the FAB and plate (if that is the correct term).
The E-3450 dimensions are 7.75" OD, 6.25" ID and 2.5" H.
What would you say is the concern with the 3450 if it is slightly smaller than the A version? It is entirely possible that the previous owner (I'm not the builder, or even the 2nd owner) revised/added that E-3450 part number to the POH.
Edit. The Van's site just says it is an E-3450.
O-360/O-540 Filter Element
Part Number = E-3450
Price = $32.00