On mine there are two ports on the head, I do not have one on the block. They are near the front and about mid way back. The holes in to the head are 1/2 NPT, or atleast 1/2 works great. I was told to use brass, so it will give before the head, just in case. They look alot like the head bolt locations. I have almost mistaken them a couple of times when I get in a hurry.
The sending unit follows the gauge on most swaps. IE.... to get a 2F stock temp gauge to work you would need a 2F sensor. I am sure this applies to F vs 2f and I assume it follows to 3F also. Location is hidden with a 3FE but I bet it would screw right in. AFAIK if it screws in and the gauge matches the sender you are there.
[quote author=dd113 link=board=1;threadid=4509;start=msg33808#msg33808 date=1061491995]
AFAIK if it screws in and the gauge matches the sender you are there.
That's what I'm hoping. Yes, my guage is the 2F guage in my 40. The 3F-E head looks almost identical to the 2F, but I don't have the 2F in there of course any more and just didn't pay too much attention; need to look tonight as to which screw/cap/plug to pull in order to put a 2F sensor.
The sensor wires were those that hooked to the two-pole disconnect on the 40's center firewall, no?