Have a 1975 350 and am converting it to TPI. When I went to install the oil pressure sending unit, the hole above the oil filter is threaded but blind. I am assuming that is where the sending unit would thread into? Or is the it non drilled hole lower and to the left?

Can I just use a small bit and drill through into the passage? If not I will just get some fittings and run it off the hole behind the intake manifold.

 

No that is not the oil pressure sender hole. That's the boss for the clutch Z-bar pivot ball.

I can't see enough of the block to be sure, but the undrilled spot may be where it goes. The bolt hole CERTAINLY is not, however.

 

I went ahead and found an assortment of brass fittings to make the dash gauge sending unit/OPSU/mech. gauge work off the oil hole behind the intake. It is easier that way.