Cudaman, Your not correct. The cast bell house used what is shown. Measure your bellhousing bolt hole thickness 4spd or auto. The hole above the starter has a much thicker area requiring a longer 3/8" bolt. The 727 used the captured washers style with the cup ridge on the head fully threaded, not the same for a 4spd in a cast bellhousing. Now 71 up where aluminum bell house used I am not sure. Here is the tooth washer that was used on the bolts that mated transmission to bell house (NOT bellhousing to block). I have seen them on cast 4 speed bolts. That transmission bolt is another style also. Too much of anything will work, and folks mismatched stuff in the day. But we are talking about three different bolts right now. Auto to block, bellhouse to block, and 4spd trans to bellhousing. All three are different styles bolts and washers at least 70 and down.

If you use a shorter 3/8 bolt (1 1/4) in that hole above the starter you have insufficient thread to meet design criteria for thread engagement in a blind cast iron hole and you risk pulling threads out of the block if you over torque it..