I am replacing my 86 305 with a the 350 Ho from gmgoodwrench. I have heard a number of times that the flexplate has to be change in some applications. My motor came with a one piece rear main seal, and I know that flexplates differ between the one piece and two piece rear main seal. IF my flexplate is alreay matched up to the one piece, will I still have to buy a different flexplate for the new motor being that it is a one piece too. And while I'm asking will the harmonic balancer be the same. Once again thanks for the help and info.