Would that adapter be based on a small block transmission or a big block transmission? Although I am guessing the big blocks were no longer in production by the time the a500 and a518’s came around.
Asking as I have seen other posts where it is stated it is easier to adapt a BB blow proof bell housing to a slant than a SB blow proof bell housing to a slant because the way the mounting bolt holes align.
If the adapter you are planning also fits a QuickTime blow proof bell to a slant that may increase the number of folks interested.
