I hope someone may be able to help, had my 1.3 samurai about a year. had to install new head due to previous owner in stalling head gasket backwards, (no oil to cam) did valve job at my buddies machine shop. drove it for a year on and off. no problems. this last month decided to do the upgrades to it. installed power steering 4.9 transfer case gears and 31x10.5x15 tires on it drove it now everything was fine until i got on the freeway wide open throttle temp gauge went to max, pulled over it dropped back down to 1/2. i installed a new t-stat and radiator. i did a block check to check for head gasket. (negative) i did find the two wires broken to the coolant temp sensor so i solder them on. could this be causing a lean condition and heating issue at wot? any ideas?

Maybe there is buildup in the block water passages?  If leak sealer is used in the coolant system it can block/restrict the radiator/block/etc.
Could also be the water pump.  Sometimes the fins on the water pump rust off and won't circulate the coolant good enough.
The temp sensor shouldn't cause it it to run lean.  If it did, it should run hot all the time, not just at freeway speeds.
If the overheating started right after you put the bigger tires on, maybe the coolant system was just good enough to keep it cool, but then the added drag of the bigger tires causes the engine to work just hard enough for it to run hot.

You should also check the fan clutch, if it's not locking on it might
not be getting the cooling air through the radiator to keep cool

Uhh - fan clutch shouldn't be an issue - at least not at free way speeds - the forward motion of the vehicle will usually provide enough air flow.

Like Skyhi says - I would give the cooling system a once over - it was probably marginal and the additional loading of the larger tires has pushed it over the edge.

I know it shouldn't be, but I had issues with an electric fan not pulling
enough air at freeway speeds, but it was pulling thru the intercooler
also, but just check it out to be sure, cover all the bases that way

the fan clutch is good i took it apart 6 months ago put some silicone paste in it because it was getting warm at idle, the weird thing is i pull over the gauge goes back to 1/2 in 2 minutes. i installed a aftermarket gauge when the factory gauge goes up to the top it is reading 210 which isn't too high still a little more than i want. i have good flow when the t-stat opens but i may still pull the water pump off and look at it or replace. at idle and around town the thing runs 1/2 all the time it is just on the freeway. i may look into airflow and see if maybe bumper, jack or aux lights may be hurting the air flow but this has not changed. i am looking for a 1.6 16v vehicle to do the swap.