Welcome to the forum, '41 Ford is a sweetie. I am a traditionalist and there is just one engine to put in that car...a flattie merc (a 312 Y block would be acceptable). As far as parts go i'd be talking to Dick Spadaro; Bob Drake (if they went out of business thier website would redirect you to whomever bought the inventory and patterns etc); Joblot Automotive has a good inventory of nos stuff too. The commercial people like Macs; LMC; Dennis Carpenter will sell you the finest in reproduced parts that may or maynot work as intended.
Search ebay and start purchasing every piece of NOS stuff you can find. I might have your heater/defroster switch panel if you need one.
Back to the engine, there is nothing like the sound of a hot rod 40 coupe - it is legendary. And that sound comes from a stroker merc flattie, a close second is the Y block. Got to have a manual transmission. Either engine will idle about 450 rpm and sound just like a chriscraft idling at the docks. That is priceless.