Gauge Reads Hot, Rad Temp OK???

I had the same trouble and used the sender unit from my 318 as it matched the gauge and have no problem now it seems that the resistance is wrong for the gauge with some of the after market senders , I also use a capilary type temp gauge in the top hose of the rad " just in case " to check on the dash one when the temp in the mec gauge reads 180f the dash one is about halfway so you need to use the origional sender unit hope this helps