I found a great place for an oil temp sender when I was doing my rebuild and I though I would share. It's on the oil filter housing and is the same size as the oil drain plug. Check it out in the pic below.
I don't know why the image does not appear. It won't let me upload it again, or a different one. Perhaps there is a server error. If you want a copy of the pic, PM me with your e-mail address and I'll send it over.Rob.
It's M12x1.5 That port goes into the oil filter supply (pressurized) so it's no good for a return port. Better to weld an aluminium pipe in the oil pan so you don't have to use a pump.