Sully;
You can use a "T-fitting" on the oil pressure line. If memory serves me correctly, the `70 L78 (and LS6) has the temp sender in the drivers side cylinder head, correct? If so, does your car have a 163 intake or a 569? If it has a 163, there should be a "spare" boss to use to add the aftermarket temp sender. I don't think the 569 has a spare boss, so you would have to go to the pass. side head to install the aftermarket sender there...provided there isn't anything occupying that space already (can't remember what/if anything goes there on `70 cars).
HTH. (I *think* I got all that right?
)
Eric