Application
The "T" or mushroom shaped adapter is the converter adapter. The small end presses into the rear of the V6 crank and the larger I.D. then serves as the pilot for the center hub of the 350 torque converter.
GM used 2 bolt circles for their torque converters (10.75" and 11.5") and most V8 flywheels are double drilled to accept either bolt pattern. Some heavy duty applications, like TH400 big block trucks, used the larger bolt pattern. The V6 flywheel should share the standard small bolt circle of the TH350 converter.
On some applications it may be necessary to drill new (or slot the existing) holes in the V6 flywheel to match the torque converter used. The pilot adapter keeps the converter centered in the rear of the crankshaft, the bolts do not perform that function. It is not a difficult operation, and can be accomplished at home with a drill press, or by any competent machinist. Instructions are included.
The small round machined piece is the center adapter for the torque converter pilot hub. The fastener pictured is a special flush head bolt which must be used on the lower passenger side corner of the adapter for clearance in the dowel pin area.