Where to get a 904 flexplate

As far as I know, there is not an aftermarket "heavy duty" type flexplate available. It is posssible to use a smallblock flexplate, but one crank hole does not lineup. The hole can be slotted, or welded and redrilled. It is off about half the hole diameter. Also, I don't know if there is an aftermarket flexplate available for the early crank (1967 down). The center hole on the early cranks is smaller.

You can see pics here. Scroll down the page.
http://www.slantsix.org/forum/viewtopic.php?p=294850#294850