Not exactly...........273 mounts need work in order to work on 340/360 engines.
340 mounts don't work in an early"A", or at least not with out a lot of work to the "K" member/engine brackets.
I really don't understand why this is so hard.......info for putting 340's/360's into early "A's has been around for over 40 years; developed by the people who designed and built the cars/engines, and made available as tech service bulletins for US, the hot rodders.