I ran a 1957 Chev 210 with a 409 C/Gas in 1966-67. The 396 was too new and too $$$ for most to afford but when they started showing up they ate the 409's alive.. I'v never heard of that swap. Wonder if it was a stroker kind of thing.
If not it seems like a step backwards. The 409 lower end was always nice to me, not so for the head gaskets.