Thanks, kewljay. I am getting my reading via the 89 gauge. I had intentions of running my original sender until I read that the 3 wire F-body sensor/sender would work. I wanted to keep it as clean as possible, and I heard that using the passenger side head for the 89 temp sender would create clearance problems with the rearmost spark plug wire. If it's readings are extremely inaccurate, I will just add the old sender.
I haven't wired up the obd2 plug or the check engine light yet. When I do I'm sure I'll get a good reading through a scan tool. Until then perhaps I'll try an infrared temp gun to give me an idea if it's actually getting as hot as I think it is.
1989 K1500, 33's, LQ4 swap in the works
1991 Mustang GT, Solid lifter 347, GR40 suspension
1972 Triumph Tiger hard tail bobber