Factory temp gauge problem

[briank]

I have a problem with my 70 jimmy 350 4bbl factory temp gauge problem. Gauge reads high after driving awhile....it basically pegs hot but it is not running hot. Engine is not original and has been replaced in 85 or so . Guy I got from recently said gauge was reading fine until he had a edelbrock intake...1806 carb with electric choke and a msd hei distributor. He said since all that was installed it reads high but he checked with a thermal gun and said its fine. Any ideas what to check? I have shop manuals but since the engine isnt original and wiring has been messed with Im at a loss. Temp sending unit is new and the same one he said worked prior to all the other work. On pass side I did notice a green wire and a black wire cut that may have been the original temp sending unit wires. Now the temp sending unit is on the drives side with a single wire running towards the firewall.