i've seen somewhere that the tooth count on the ring gear for the 350/v6 is 161 teeth, and that the 455 is different. also that there is a thickness issue that caused somebody some trouble. don't know anything about the thickness issue, could somebody chime in here? couldn't you use a 350 starter to match up to the ring gear? mounting is the same isn't it? any other differences ?
Although you can't swap the flexplates, the starters do interchange. I used my old 350 starter on my 455 for almost a year till I ponied up the $$ for a good mini-starter.