i got an small block year is 86-94 so it's an one
peace rear seal 350 block.the install guide that
came with my small block says to use an late model
350 weighted flex plate.i dont know what weighted
means??? i asked the company for an part number.
flex plate part#490-10-025 hays said it an 86-94
one peace external bal 158 tooth.i cant get hays
parts only B&M and TCI from my parts guys.
so what im asking is what does weighted mean
and can i use an b&m flex plate part number 20239
or TCI part number 399773. these two are the same as
the hays but 168 tooth and on all of the 3 flex
plates web sites hays b&m and tci there is no
refrance to any kind of weighted flex plate  

When GM went to 1 piece seals the flexplate mounting flange shrunk to 3.00 inches so they added a  counterweight to make it a external bal.flexplate to make up for it.But still uses a internal harmonic balancer.    WIEDER