4-spd install in 74 TA, clutch linkages bellcrank bracket mounting

[BAD74TA]

Hello  looking for input on installing bellcrank (z-bar} bracket for a Auto to Manual swap.  Car was automatic, but looks like factory holes were in the frame for whatever transmission the car would get.

In mounting the bellcrank bracket on the left frame outside, I plan to use 5/16 (8MM) self-taping screws.  Questions is should I tap threads into the hold first, or can I just use an impact wrench and drive the sefl-tapping screws in.  The pre-drilled holes have never been used and the hole, while drilled completely through, appears to only have punctured the frame and not drilled through as to make a clean hole, if that makes sense.

Also for the opposite side of lelft rail frame, will be installing the bracket for the neutural/reverse rod.  Again there are pre-drilled holes, but the three on the inside of the frame are nice clean holes, whereas the three holes on the outside are not as clean drilled through.  So I'm thinking I need to tap the inside frame for the bracket, and use a bolt instead of self-tapping screws here.

Thank you

[Skunkwerks]

Use the self tapping bolts that are the correct size for the pre-punched holes in the frame. Same bolts used to attach the front wheel inner wheel splash shield rear corner bracket to the frame. Will work very well as that is what Pontiac originally used.
Make sure you get the correct Pontiac Bell crank and not the Chevy one. The Chevy one will bolt up but will rub on the bell housing as the inner arm is closer for the chevy 350 to fit correctly.
The way I tell if you have the correct one is the grease zerk on an original part is closer to the middle of the tube not closer to the outer end as on the Chevy model. 
You will also need the return spring holder bracket the mounts to the frame with the same self tapper.

[BAD74TA]

Thanks for that Skunkwerks, I ended up using 5/16" tapered end screws after tapping threads in the pre-drilled holes.  I bought my 4spd conversion from a guy that said everything came from a '78 TA.  Your comment about the original vs Chevy bell-crank was good info to know.  Looked at mine, and the zerk is definitely far to one side of the bell-crank, so now I'm not sure what I have or if it will rub the bell housing as you say.  Do you know if the part from the 78 will fit my 74?  If not, guess I'm in the market for a part that fits.  I had my parts powder coated, so sure hoping I can use it.