How can I block off the hoses going to the heater box? Or put a valve in one of the hoses (which one)
Big block ,,,, No A/C ,,,Thanks

What do you want to do , stop the flow because it's hot in the car of remove the heat path completely ?

Too hot in the car, in the summer.

PLUGS in the water pump ...or caps on the tubes.

Quick and dirty way to do it is to loop a short section of heater hose on the water pump. Then you don't have to pull the nipples out to replace them with plugs.

But my hoses are different sizes.

Use the larger of the two hoses and clamp it down, she will hold.

I simply installed a ball-valve up near the firewall, in the big (3/4" line) because that was the size of the valve I found.
Works like a charm. No tools required to turn heat on and off, but you do have to lift the hood of course.
Interior is noticably cooler on hot days!!!

If you want to disable the heat but not remove it entirely, you could put in a valve on a heater hose so you can shut off coolant flow during the summer. Just in case you want to keep the heat around at the flick of a switch.

What I did with mine was my car has a valve for the heater hose that shuts off coolant flow when the heater controls are put in the strato-vent position. Vacuum switch didn't work anymore so I just ran the vacuum hose from the heater hose valve straight to the intake. Problem solved. If I wanted heat back I just unplugged the vacuum line and put a cap on.

Many cars came with a heater hose shut off valve. Just use one of those. My 1976 D200 truck had one mounted on the inner fender.

Thanks guys
I put a ball valve in and will see how it works.

OK ....BE SURE to put that valve IN the CORRECT side(the OUTLET side) of the water pump. IF you don't .... you can BLOW UP the heater core.

DON'T ask me how I know..

Try a mini ball valve that you could install at the water pump to keep it out of sight.