Question for all of you 302 owners I only have 351

I went to help a couple I have helped in the past. We are all just about crippled so we just try, lol.
They have a 68 coupe with 302. I know not 71 - 73 but same engine. We had changed out the gas tank, fuel pump and he tried to flush the cooling system. It sat for 12 years. When he put the thermostat back it leaked. I took off today and the thermostat was under the flange of the housing caused the leak. The original Ford thermostats like screwed into the housing to hold in place. No parts house we checked had them. The inside of the thermostat housing has two angles and that is where the thermostat locked into to prevent it falling down. DOES ANYONE KNOW WHERE TO GET AN ORIGINAL STYLE THAT LOCKS IN?  If you have ever changed you know the bottom bolt is in a position so you cannot use a socket. Is crazy tough to get bolt started. I am going go put a stud in and use nuts on them instead of bolt. I would be nice to have correct thermostat that actually locks into the neck you are bolting on. The old coolant in the car had turned into a gel slime and was crazy. He is going to use a prestone flush and see if it cleans up.
BTW I got my onion sets today will start on garden this weekend. That is if neck will let me. Might just did a hole and fall in. Greens and broccoli next.

The bridge on the thermostat acts as the lock, just turns enough to hold it in place. On thermostat housings that don't have the slot for it to lock into I set the thermostat into the groove and use some gasket sealer on the gasket to hold it in place while installing.

A trick I learned a few years ago is to use a couple drops of super glue to hold the thermostat in the housing.  The gel type works best.  I just use two small drops 180 degrees apart.  It will hold it tight and yet you can break it loose to remove the thermostat when needed.

I always used a bit of gasket sealer and the gasket to hold it for the second or two of trying to stick in into place.  I will have to look for these tabs and such, didn’t know they existed.  

I've always found this method to work..

We used the gasket sealer but the housing is so warped it kept coming loose. The rubber band is great idea. I do not know why they quit making the twist in thermostats they worked great never had an issue.