Putting an Escort GT motor in my Miata, what should I do with this coolant neck?
 

Here is the back of a 1.8L Miata motor:
https://www.miataturbo.net/attachmen...ine=1344289476

Here is the back of the Escort GT motor I just picked up:
https://www.miataturbo.net/attachmen...ine=1344289476

The previous owner had it in his Miata, but had a coolant re-route on it. I won't be doing a coolant reroute, I'll be putting the Miata neck on the front and run it right to the radiator. Only problem is, what should I do with the rear end? The Miata motor has a line running to the oil filter, but the Escort GT motor has one running to the to the oil filter, and one to the heater core. Should I block off that port and transfer over the coolant neck to the Escort GT motor from my old one? Or cap the bigger hole that you see? Not sure what to do with a thermostat or the coolant sensor...

Input would be appreciated. I need this done ASAP.

So the head you are taking out has a 2 bolt plate that fed the heater core and a single barb feeding the oil cooler. The head you want to install has room for the 2 bolt plate and an extra little barb on the barb that feeds the oil cooler. You need help figuring out what to do with the little extra barb?

EDIT after I reread your post:

If you don't want to do a coolant reroute, put all the ---- off your old motor onto the new one. Block off the extra barb.

Unless it is easier for YOU to cap the large hole & create a sensor hole somewhere. I would think pushing a rubber cap on a barb would be the easier solution but not the right solution. The right solution is doing a proper reroute.

Cap one of the lines, use old water neck.
What's the problem?

if none of the holes are the right size you can use silicone hose that is easier to stretch, but make sure to use good clamps on silicone (worm drive clamps with smooth liner, for example)

I think I'll go ahead and transfer over the old water neck and cap the line he has running to the heater core. Like you say TurboTim, something doesn't seem right about that, but I think its the only way to go. The car needs to be done by this weekend, so I don't have time to do a coolant reroute, but its nice to know that I can do one pretty easily when I have time. I just hope it's not too pressurized back there because the last thing I want is a leak once everything is in.

I'd drill and cut threads into the head, next to the thermostat area. That sensor also fits in the plug above the nipple, below the intake cam.